Remove OpenGL ES 1.1 support

We haven't depended on OpenGL ES 1.1 support for years now and if we can
remove the need to support GL's legacy fixed function apis then we may
simplify some parts of Cogl.
Remove ARBfp support

For simplicity we would like to only support GLSL based progends even
though it's still quite possible that the ARBfp backend may be slightly
faster in some cases.
Remove support for GL's legacy fixed function apis

This removes the GL fixed function vertend, fragend and progend since we
don't have any need to support non programmable GPUs and since it
reduces the number of code paths we maintain.

This adds "nop" backends so that for now, we continue to keep support
internally for selecting pipeline backends at runtime.