In `class OS_Unix` the arguments in the `execute` method are converted
to UTF-8, but in the `main` program's method they're inserted into a
wide-char `Vector` before translating them from UTF-8 and thus the
non-ASCII characters are lost.
This fix converts the `argv` elements to UTF-8 using `String::utf8`
before inserting them in the `Vector`.
-load() was in the GDScript docs but missing in the scripting-different music for platformer 2D and 3D
-fix how documentation is generated, built in doc browser should be always up to date
-copypaste, scrolling, etc in builtin doc
-built-in scripts get saved now (though debugger may not always work on them)
-Theme can be set to controls as a property
