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

A simple 1st person camera... still requires some work...

raylib uses spaces between '+' and '-' signs but not between '*' and '/'
signs, it's a chosen convention

Fixed use-after-free in DestroyLight

Set makefile to default OpenGL 3.3 compilation

Corrected lighting system crash and VR variables not found...

Matching the same stereo rendering result given by Oculus PC SDK for
Oculus Rift CV1 is very difficult because hardware has changed a lot and
DK2 distortion shader and parameters don't fit on CV1. Some custom
parameters have been calculated to simulate kind of CV1 stereo
rendering. Further work is required on this point.

Simulator configuration is directly obtained from VR device parameters!

- Embedded VR distortion shader
- Ready to support multiple VR devices
- Fallback to VR Simulator if device not ready
- Support mono rendering over stereo rendering

-IN PROGRESS-

...to avoid dynamic conditions on for loop (lightsCount) on standard
shader, it seems GLSL 100 doesn't support that feature... on some GPUs
like RaspberryPi...

Stereo rendering has been moved again to Begin3dMode() and End3dMode(),
it has some limitations but makes more sense...