The support for the scissor test has been implemented for clearing as well as for triangle clipping.
The implementation for lines and points is still missing.

I also removed the 2D clipping of lines that used the Cohen-Sutherland algorithm, opting instead to always use the Liang-Barsky algorithm in all cases.
This simplifies the implementation, and the 2D version would have caused issues when interpolating vertices in the future if we want to implement additional features.

- `glDepthMask`
- `glColorMask`

Several depth and color formats have been added for the framebuffer.

8-bit, 16-bit, and 24-bit formats are now available for depth.

RGB 8-bit (332), RGB 16-bit (565), and RGB 24-bit (888) formats are now available for color.

Alpha support is no longer present for the framebuffer at the moment, but it can easily be restored by adding the formats and reinterpolating the alpha in the areas that do not perform color blending.

Additionally, this commit brings performance improvements.

+ review unorm/float conversion

to be closer to the OpenGL API

+ tweak function names

Also replace the triangle rasterization functions with macros that generate specific functions for each state of the rendering system.
Also, add the OpenGL definitions in order to add a binding for rlgl.