Lots of fixes importing SDL source wholesale into a new iOS project

--HG--
rename : src/libm/math.h => src/libm/math_libm.h

src/video/x11/SDL_x11opengl.c

@@ -19,6 +19,9 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 #include "SDL_config.h"
+
+#if SDL_VIDEO_DRIVER_X11
+
 #include "SDL_x11video.h"
 #include "SDL_assert.h"
 
@@ -610,4 +613,6 @@ X11_GL_DeleteContext(_THIS, SDL_GLContext context)
 
 #endif /* SDL_VIDEO_OPENGL_GLX */
 
+#endif /* SDL_VIDEO_DRIVER_X11 */
+
 /* vi: set ts=4 sw=4 expandtab: */