clean up audio chiptunes support

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

...on Android

Fix mistake in the make file

Moved all external libraries used by raylib to external folder inside
raylib src. Makefile has already been update and also the different
includes in raylib modules.

Android build system has been simplified and now is included in src
folder, like other build systems.

Trying to find the best way to integrate Oculus support into raylib,
making it easy for the user...

Not functional yet...

Internal modelview and projection matrices can be replaced before
drawing.