* Remove PLATFORM_RPI

* remove build artifacts

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Co-authored-by: MichaelFiber <michael@cubeofb.org>
Co-authored-by: Ray <raysan5@gmail.com>

Now rlgl uses the `Matrix` type, just make sure it has been previously defined somewhere... I don't like this approach but it's probably the easier one for the users... still looking for a better solution... maybe using something like
`#define MATRIX_TYPE`, so it can be checked in other modules.

* Added support for additional mouse buttons

* Renamed mouse button enum

Co-authored-by: Lambert Wang <lambert.ww@gmail.com>

- Some rlgl functions have been moved to core
 - Some functions have been made internal to rlgl
 - rlgl functions prefixed with rl*()

Some enums values have been renamed to be more consistent and also provide a more detailed description:
 - ShaderLocationIndex:    LOC_VERTEX_POSITION -> SHADER_SHADER_LOC_VERTEX_POSITION
 - ShaderUniformDataType:  UNIFORM_VEC2 -> SHADER_UNIFORM_VEC2
 - MaterialMapType: MAP_ALBEDO -> MATERIAL_MAP_ALBEDO
 - PixelFormat: UNCOMPRESSED_GRAYSCALE -> PIXELFORMAT_UNCOMPRESSED_GRAYSCALE

This function was renamed for consistency in raylib 3.0, just unified all examples to use TextFormat() instead of FormatText()