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.
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.
