From Anders F Bjorklund:

When switching to "UNIX-style paths" as needed for the new includes,
including <GL/gl.h> and <GL/glu.h> doesn't work anymore on Mac OS...

The two headers are really located in the OpenGL SDK 1.2 CFM like this:
OpenGL:Headers:gl.h
OpenGL:Headers:glu.h

There are also some compat copies, that *used* to work with Mac paths:
OpenGL:Headers:GL/gl.h
OpenGL:Headers:GL/glu.h

The easiest fix is to make SDL_opengl.h include the proper header names,
by adding a special case for the MACOS platform in addition to the MACOSX

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401626

include/SDL_opengl.h

@@ -37,6 +37,9 @@
 #if defined(__MACOSX__)
 #include <OpenGL/gl.h>	/* Header File For The OpenGL Library */
 #include <OpenGL/glu.h>	/* Header File For The GLU Library */
+#elif defined(__MACOS__)
+#include <gl.h>		/* Header File For The OpenGL Library */
+#include <glu.h>	/* Header File For The GLU Library */
 #else
 #include <GL/gl.h>	/* Header File For The OpenGL Library */
 #include <GL/glu.h>	/* Header File For The GLU Library */