update SDL port to support OpenGL
need to separate out SK_BUILD_FOR_MAC when we need to know where certain OS
headers are, and SK_BUILD_FOR_SDL when we are choosing an SkOSWindow variant...



git-svn-id: http://skia.googlecode.com/svn/trunk@190 2bbb7eff-a529-9590-31e7-b0007b416f81
5 files changed