Make ARB_imaging (and other compatibility) enums that are removed actually removed.
As it stands, if you iterate over enums from a core extension, you get all enums, even if they're not all from core extensions. Same goes for compatibility.
ARB_imaging is the first core OpenGL extension. But it has a bunch of enums that are non-core. They should be removed when making a core OpenGL profile, but only for extensions that were not explicitly requested.