Merge edit_form_advanced and edit_page_form hooks

[solarissmoke]

In the era of custom post types, having to register one hook for pages (edit_page_form) and one for all other post types (edit_form_advanced) to add stuff to the post editor seems a bit weird. I think that these should be consolidated.

I guess the most backward-compatible way would be to deprecate both of these hooks and add one that fires for all post types, and passes the post type as an argument?

Something like this

The introduction of the edit_form_after_editor (r22446) resolves the issue that I had, so unless anyone still feels that having a separate hook for pages is unnecessary, this can probably be closed.

There are a *lot* of places that fire different hooks for pages versus everything else. Not worth fixing this one without a systematic approach.