Using `misc/scripts/fix_headers.py` on all Godot files.
Some missing header guards were added, and the header inclusion order
was fixed in the Bullet module.
- Make sure to search the mono installation directory for the right architecture in the windows registry.
- Do not build GodotSharpTools directly to #bin dir. Instead build to the default output path and copy it. This way we avoid MSBuild adding files we don't want to #bin.
- Add hint path for MSBuild in OSX.
- Copy shared library on Unix if not statically linking.
- Use vswhere to search MSBuild and search for 14.0 tools version in the registry instead of 4.0.
- SCons will only fallback xbuild when msbuild is not found if 'xbuild_fallback=yes' is passed to the command.
- Use mono's assembly path as FrameworkPathOverride if using with system's MSBuild (not mono's fork).
- Cleanup.
