Review exposed #defines and allow user re-defining

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.

src/raylib.h

@@ -99,8 +99,6 @@
 #define DEG2RAD (PI/180.0f)
 #define RAD2DEG (180.0f/PI)
 
-#define MAX_TOUCH_POINTS        10      // Maximum number of touch points supported
-
 // Allow custom memory allocators
 #ifndef RL_MALLOC
     #define RL_MALLOC(sz)       malloc(sz)