Avoid running glGetString during import, but it's too fragile

Basically anything which takes an extension or similar function and 
does a boolean test on it is going to cause a glGetString() operation,
and that will crash on OS-X. There is definitely some code in the 
images module that does bool(imageFunction) where it really should
not be doing so (i.e. on import).  That should work now, simply because
the functions *happen* to be core (version XXX).
Wrong, do *not* set extension NULL, is_core is sufficient
Make displayed error messages much longer before we truncate them (otherwise we often lose the message we spent so much effort formatting for the user)
Regenerate accelerate wrappers with cython 0.20
Import of array module messed up config-flag system
Fix for ctypes pointers showing up as pointers-to-pointers
Get the GLES imports working, though still don't have any test code
Remove the egl test code, as to get it working I used GPL code
Missing import to provide the GLES2 entry points in GLES3
Update auto-generated files to latest khronos