Merge pull request #213 from Bigpet/master

Compile fix for VS (doesn't like implicit `u64 *` to `unsigned long*`)
Mac OSX: fix includes & add missing functionality
Mac OSX: use __thread for thread-local storage
add info for Mac OSX
move clock_gettime() into GNU.cpp
detect Mac OSX and Windows, fall back to Linux
Merge pull request #214 from kaazoo/master

Add compilation support for Mac OSX
fix OpenGL includes for Win32
more compact precompiler checking