TINYGL: Dirty rects system.

This PR contains an implementation of dirty rects system.
You can find more information behind the design and implementation in the following blog posts: 
http://subr3v.blogspot.co.uk/

No I mean if we decide to change the implementation of gl_malloc and gl_free (either by using a dedicated memory region or something else, or just change the allocators, or if we want to track which module is taking a certain amount of memory)