updateAudioContext is almost done

Ease of use considered in api and channels are more convenient as
unsigned char type.

Removed BeginDrawingEx()
Added Begin2dMode() and End2dMode()

First stage of audio API update

Improve DXT-ETC1 support on HTML5

Hiding the struct from user should protect from accidentally modifying
the mix channel. This could cause serious errors down the road.

Look over changes and give feedback please.

quick fix (module audio support)

There is still an issue where audio will cut off after a brief moment

Boolean errors

Added proto version of jar_xm

This is an early draft, needs lots of work. Still need to figure out way
to calculate total length of song. This is hard because xm tracks stream
out zeros when done, only position in track can be found. Position does
not give any direct value of how much more time is left. I think that by
setting the loop count to 1 and seeking until the end I can total up the
number of samples and come up with a length.

... easy code porting, transalating them to touches and gestures
internally.

Removed function SetCustomCursor(), it can be managed by the user.

I decided it is redundant and could be confusing (when mixed with 3D
drawing). It's not KISS.

NOTE: It requires a depth texture as input, it should be configured on
rlgl, by default RenderTexture (fbo) uses Depth Renderbuffer instead of
Depth Texture. Check rlglLoadRenderTexture()

Fix Makefile files

I've added .PHONY targets and fixed "clean" recipe.

Only defaultShader required, set default value for vertex color
attribute if not enabled and fragColor uniform