There are multiple #define values around raylib, usually not exposed for redefinition, just reviewed all of them to allow users redefining them on compile time if required.

Also, multiple #define have been renamed and commented.

Just for clarification, no plans to remove libc dependency, just did some code analysis to see how much raylib depend on stardard C library. My conclusions:

 - stdlib.h: primary dependency is for malloc() and free()
 - stdio.h: primary dependency is for FILE access, maybe it could go through a custom ABI?
 - string.h: just around 8 functions required
 - math.h: just around 8 functions required
 - others: 1-2 functions required for some other headers

* [core] REDESIGNED: Implement global context

* [rlgl] REDESIGNED: Implement global context

* Reviewed globals for Android

* Review Android globals usage

* Update Android globals

* Bump raylib version to 3.0 !!!

* [raudio] REDESIGNED: Implement global context

* [raudio] Reorder functions

* [core] Tweaks on descriptions

* Issues with SUPPORT_MOUSE_GESTURES

* [camera] Use global context

* REDESIGN: Move shapes drawing texture/rec to RLGL context

* Review some issues on standalone mode

* Update to use global context

* [GAME] Upload RE-PAIR game from GGJ2020 -WIP-

* Update game: RE-PAIR

* [utils] TRACELOG macros proposal

* Update config.h

Monotonic time since InitWindow() could be retrieved with this function.

There have been two problems:

* GLFW itself was compiled with the definitions for compiling
_against_ GLFW (fixed by removing requirement for external glfw)

* rglfw.c was being compiled as C code, although it includes
Objective C files.

This _might_ break the Windows build, needs to be checked.

Fixes #391, but as noted I'd prefer though a separate source directory
and build script for GLFW.

Feature macros need to be defined before #including any headers,
preferably through the build system, but this is good enough.

Fixes a compile error on my fork's Travis CI.

If we compile with c99 without gnu extensions (gnu99) we need this
define, to have CLOCK_MONOTONIC and similar macros available

Reviewed some Vector3 functions
Added auxiliary Clamp() function

Working in modules configuration flags...

Required by gestures example....

Use instead: IsGestureDetected()

Using normalized [0..1] input points

Corrected Android processing for some inputs (BACK button, VOLUME
buttons)
Redesigned Gestures system (some work still required)
SetEnabledGestures() - Only support desired gestures (requires some
review)

Now gestures system can be used as standalone module