[rlsw] Some platform fixes

[Bigfoot71]

• Fixes compilation errors for DRM.
• Handles resizing for SDL and WIN32.

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A little validation for WIN32 would be preferable; I don't have a Windows machine to test on, but I simply added this to HandleWindowResize:

#if defined(GRAPHICS_API_OPENGL_SOFTWARE)
swResize(clientSize.cx, clientSize.cy);
#endif

Also, I had added it for RGFW, but when I tried to test it I realized that software rendering is not supported, black screen, so I didn't do anything.

[Bigfoot71]

Oops, branch issue