AL/alext.h is not supported on html5 OpenAL implementation, just
replaced by the defines used in audio module

Only using raylib required extensions... it could be further reduced!

Adapted shaders for OpenGL ES 2.0

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

Some shader calculations are now pre-calculated because some math
functions doesn't exist in glsl 110.

Fix Android template with 1.5 raylib features (audio streaming, gestures)

clean up audio chiptunes support

... and switch from debug build to release

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

...on Android