Add support for EGL.

This totally replaces the getprocaddress and dlsym code, which was
basically just stubs up until now.  The is_glx/is_egl() is also
dropped -- they weren't doing anything, and the only false answer they
could give is if the dlopen were to fail.
Drop a bit of commented out python.

It was used in debugging before I figured out I needed to resolve
aliases late.