the tile cursor did not follow the mouse cursor, and the tile grid was displayed wrong,
because the forward_canvas_draw_over_viewport function used the wrong xform and thus its
map_to_world is not the inverse of the mouse interactor world_to_map, making the tiles
draw from 0,0 of the screen instead of 0,0 of the tile map (which is in a different place)
Fixes the following GCC 8 warnings:
```
core/image.cpp:730:44: warning: 'mip1_weight' may be used uninitialized in this function [-Wmaybe-uninitialized]
core/image.cpp:293:20: warning: 'mip2' may be used uninitialized in this function [-Wmaybe-uninitialized]
core/image.cpp:293:20: warning: 'mip1' may be used uninitialized in this function [-Wmaybe-uninitialized]
editor/audio_stream_preview.cpp:58:19: warning: 'vmax' may be used uninitialized in this function [-Wmaybe-uninitialized]
editor/audio_stream_preview.cpp:85:19: warning: 'vmin' may be used uninitialized in this function [-Wmaybe-uninitialized]
editor/editor_themes.cpp:306:53: warning: 'preset_contrast' may be used uninitialized in this function [-Wmaybe-uninitialized]
editor/plugins/animation_blend_space_2d_editor.cpp:459:27: warning: 'prev_idx' may be used uninitialized in this function [-Wmaybe-uninitialized]
editor/plugins/animation_blend_space_2d_editor.cpp:443:27: warning: 'prev_idx' may be used uninitialized in this function [-Wmaybe-uninitialized]
main/tests/test_oa_hash_map.cpp:57:29: warning: 'value' may be used uninitialized in this function [-Wmaybe-uninitialized]
modules/csg/csg.cpp:764:40: warning: 'max_angle' may be used uninitialized in this function [-Wmaybe-uninitialized]
modules/csg/csg_shape.cpp:1945:3: warning: 'face_count' may be used uninitialized in this function [-Wmaybe-uninitialized]
scene/3d/voxel_light_baker.cpp:1593:8: warning: 'cone_aperture' may be used uninitialized in this function [-Wmaybe-uninitialized]
scene/3d/voxel_light_baker.cpp:1592:6: warning: 'cone_dir_count' may be used uninitialized in this function [-Wmaybe-uninitialized]
scene/animation/animation_blend_space_2d.cpp:471:8: warning: 'mind' may be used uninitialized in this function [-Wmaybe-uninitialized]
core/os/memory.cpp:94: warning: ignoring #pragma clang diagnostic [-Wunknown-pragmas]
core/os/memory.cpp:95: warning: ignoring #pragma clang diagnostic [-Wunknown-pragmas]
core/os/memory.cpp:98: warning: ignoring #pragma clang diagnostic [-Wunknown-pragmas]
```
Disabled signed/unsigned warnings like for GCC/Clang
(warning C4018: '>=': signed/unsigned mismatch).
Fixes the following MSVC 2017 warnings:
```
core\image.cpp(999): warning C4804: '>': unsafe use of type 'bool' in operation
core\io\compression.cpp(178): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
editor\doc\doc_dump.cpp(226): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
scene/resources/material.h(289): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
scene/resources/material.h(298): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
editor\editor_themes.cpp(379): warning C4805: '==': unsafe mix of type 'int' and type 'bool' in operation
```
Fixes the following Clang 7 warnings:
```
editor/editor_help.h:123:7: warning: 'EditorHelpIndex::popup' hides overloaded virtual function [-Woverloaded-virtual]
editor/editor_help.h:95:7: warning: 'EditorHelpSearch::popup' hides overloaded virtual function [-Woverloaded-virtual]
editor/editor_help.h:96:7: warning: 'EditorHelpSearch::popup' hides overloaded virtual function [-Woverloaded-virtual]
editor/plugins/curve_editor_plugin.h:141:15: warning: 'CurvePreviewGenerator::generate' hides overloaded virtual function [-Woverloaded-virtual]
editor/plugins/script_editor_plugin.h:70:7: warning: 'ScriptEditorQuickOpen::popup' hides overloaded virtual function [-Woverloaded-virtual]
editor/quick_open.h:69:7: warning: 'EditorQuickOpen::popup' hides overloaded virtual function [-Woverloaded-virtual]
main/tests/test_io.cpp:53:15: warning: 'TestIO::TestMainLoop::input_event' hides overloaded virtual function [-Woverloaded-virtual]
servers/audio/effects/audio_effect_record.h:69:15: warning: 'AudioEffectRecordInstance::process_silence' hides overloaded virtual function [-Woverloaded-virtual]
core/os/memory.h:119:2: warning: destructor called on non-final 'ContextGL_X11' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
core/os/memory.h:119:2: warning: destructor called on non-final 'EditorScriptCodeCompletionCache' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
core/os/memory.h:119:2: warning: destructor called on non-final 'Engine' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
core/os/memory.h:119:2: warning: destructor called on non-final 'PhysicalBone::JointData' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
core/os/memory.h:119:2: warning: destructor called on non-final 'VisualServerScene' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
core/os/memory.h:119:2: warning: destructor called on non-final 'VisualServerViewport' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
```
Fixes the following Clang 7 warnings and bugs:
```
editor/plugins/curve_editor_plugin.cpp:208:69: warning: logical not is only applied to the left hand side of this comparison [-Wlogical-not-parentheses]
editor/plugins/curve_editor_plugin.cpp:214:43: warning: logical not is only applied to the left hand side of this comparison [-Wlogical-not-parentheses]
```
Changed according to @Zylann's suggestion on
https://github.com/godotengine/godot/pull/22593#discussion_r221699573
Fixes the following Clang 7 warnings:
```
drivers/gles3/rasterizer_scene_gles3.cpp:1260:10: warning: variable 'target' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
drivers/gles3/rasterizer_scene_gles3.cpp:1280:10: warning: variable 'target' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
drivers/gles3/rasterizer_scene_gles3.cpp:1281:10: warning: variable 'target' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
drivers/gles3/rasterizer_scene_gles3.cpp:1282:10: warning: variable 'target' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
drivers/gles3/rasterizer_scene_gles3.cpp:1286:5: warning: variable 'target' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
editor/editor_properties_array_dict.cpp:982:15: warning: variable 'change_index' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
editor/editor_properties.cpp:2655:6: warning: variable 'lt' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
editor/settings_config_dialog.cpp:367:11: warning: variable 'current_search_box' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
```
Namely:
[-Wunneeded-internal-declaration]
[-Wunused-comparison]
[-Wunused-const-variable]
[-Wunused-function]
[-Wunused-private-fields]
Fixes the following Clang 7 warnings:
```
editor/plugins/script_editor_plugin.cpp:1417:20: warning: function '_find_node_with_script' is not needed and will not be emitted [-Wunneeded-internal-declaration]
editor/scene_tree_dock.cpp:1859:14: warning: function '_find_last_visible' is not needed and will not be emitted [-Wunneeded-internal-declaration]
modules/gdscript/gdscript_parser.cpp:7838:19: warning: equality comparison result unused [-Wunused-comparison]
scene/resources/mesh.cpp:549:35: warning: unused variable '_array_types' [-Wunused-const-variable]
scene/resources/mesh.cpp:563:18: warning: unused variable '_format_translate' [-Wunused-const-variable]
drivers/gles3/rasterizer_scene_gles3.cpp:54:28: warning: unused function 'store_transform2d' [-Wunused-function]
core/io/file_access_network.h:50:6: warning: private field 'ml' is not used [-Wunused-private-field]
core/io/file_access_zip.h:93:14: warning: private field 'archive' is not used [-Wunused-private-field]
core/io/resource_format_binary.h:122:6: warning: private field 'bin_meta_idx' is not used [-Wunused-private-field]
core/message_queue.h:47:9: warning: private field 'mutex' is not used [-Wunused-private-field]
main/tests/test_gui.cpp:63:11: warning: private field 'control' is not used [-Wunused-private-field]
modules/gdscript/gdscript_parser.h:558:7: warning: private field 'completion_static' is not used [-Wunused-private-field]
platform/x11/os_x11.h:148:11: warning: private field 'ip_unix' is not used [-Wunused-private-field]
platform/x11/os_x11.h:180:7: warning: private field 'net_wm_icon' is not used [-Wunused-private-field]
platform/x11/os_x11.h:189:6: warning: private field 'audio_driver_index' is not used [-Wunused-private-field]
platform/x11/os_x11.h:190:15: warning: private field 'capture_idle' is not used [-Wunused-private-field]
servers/physics/body_pair_sw.h:79:6: warning: private field 'cc' is not used [-Wunused-private-field]
servers/visual/visual_server_raster.h:62:7: warning: private field 'draw_extra_frame' is not used [-Wunused-private-field]
```
Fixes the following Clang 7 warnings:
```
core/object.cpp:44:1: warning: '_ObjectDebugLock' defined as a struct here but previously declared as a class [-Wmismatched-tags]
core/variant_call.cpp:43:1: warning: '_VariantCall' defined as a struct here but previously declared as a class [-Wmismatched-tags]
drivers/gles3/rasterizer_storage_gles3.h:765:2: warning: 'MultiMesh' defined as a struct here but previously declared as a class [-Wmismatched-tags]
editor/editor_node.h:794:1: warning: 'EditorProgress' defined as a struct here but previously declared as a class [-Wmismatched-tags]
modules/bullet/rigid_body_bullet.h:230:17: warning: class 'KinematicUtilities' was previously declared as a struct [-Wmismatched-tags]
modules/bullet/space_bullet.h:60:1: warning: class 'btSoftBodyWorldInfo' was previously declared as a struct [-Wmismatched-tags]
scene/resources/world_2d.cpp:40:1: warning: 'SpatialIndexer2D' defined as a struct here but previously declared as a class [-Wmismatched-tags]
scene/resources/world.cpp:39:1: warning: 'SpatialIndexer' defined as a struct here but previously declared as a class [-Wmismatched-tags]
servers/audio/reverb_sw.cpp:60:1: warning: 'ReverbParamsSW' defined as a struct here but previously declared as a class [-Wmismatched-tags]
thirdparty/bullet/BulletSoftBody/btSoftBody.h:43:1: warning: 'btSoftBodyWorldInfo' defined as a struct here but previously declared as a class [-Wmismatched-tags]
```
Also finally move freetype to its own env and disable warnings for it.
Still needs some work to fix the awkward situation of the freetype and
svg modules used in scene/ and editor/ respectively.
* Orthogonal cameras don't have an FOV that's "near zero". Or zero, or any number of degrees. It's not a measurement of degrees, it's just a fixed width. This comment is more accurate. Also, "terrible" is a better word than "awful" here.
* While I'm editing this file, the "String ortho" variable name could be more intuitive, so I've changed it to "view_mode".
Minor nit-picky changes, I know, but I found it so I may as well improve it.
