Now it works great with reviewed maths

Some other tweaks...

Now it should be coherent with OpenGL math standards

Exposed some raymath useful functions to raylib API

Still shader dependant, locations set should be moved out

Corrected compilation for OpenGL 1.1
Review mesh data uploading to GPU

Moved PBR material loading to example, right decision?

...to avoid possible conflicting symbols

Moved to custom example, now raylib only supports simulated VR
rendering.
Oculus code was too device dependant... waiting for OpenXR.

Working in modules configuration flags...

Lighting is implemented as a raylib example now

Actually, renamed ReadTextFile() from rlgl and make it public

- Renamed WritePNG() to SavePNG() for consistency with other file
loading functions
- Renamed WriteBitmap() to SaveBMP() for consistency with other file
loading functions
- Redesigned SaveBMP() to use stb_image_write

log2() is not available in some standard C library implementations

texture.mipmaps value needs to be updated, so, texture must be passed by
reference instead of by value