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

Still thinking about the best way to manage this...

Now it's easier for the user! Just init Oculus device and get stereo
rendering!

It's more educational to go through new material system, so, I decide to
remove this function to avoid students confusion...

...to align it with standard raylib code. Final goal would be having the
same code work for every platform with no changes...

Under design... looking for the easiest and most comprehensive way for
the user to use VR...

and remove static from PhysicsThread().

and add instructions in physac examples to run it successful.

and added PHYSAC_NO_THREADS define. Improved physac example drawing
frames per second in screen.

texture() doesn't exist in glsl 100, it must use texture2D().

Trying to simulate Oculus Rift CV1 rendering without the device... for
Debug pourposes.

Not functional yet...

Still working on the sample but almost finished. Some rlgl internals
redesign required and it will be ready!

Tint color could be applied to colDiffuse... but what's the best way?
Replace it? Multiply by? A point to think about...

Functions renamed to improve library consistency