There is no OpenGL support. There is only OpenGL ES (1.1/2.0) support. GLES 1.1 headers are found from GLES/gl.h. Depending how the original OpenGL program was made there can be quite a bit of porting work to make it work with OpenGL ES.

If you'd like to use OpenGL ES easily with sdl, you can use libsdl-gles1.2 to create gles rendering context.