Change the way SDL.h is included to standard cross-platform way.
Here's the explanation http://wiki.libsdl.org/FAQDevelopment#Do_I_.23include_.3CSDL.h.3E_or_.3CSDL.2FSDL.h.3E.3F
Merge pull request #16 from poxu/master

Change the way SDL.h is included to standard cross-platform way.