Removing pads from interfaces

Glib interfaces don't need padding in order to maintain the ABI, so
removing as they are not needed.
text: Deprecate atk_text_get_text_{before,after}_offset()

https://bugzilla.gnome.org/show_bug.cgi?id=697968
text: Deprecate _END boundaries

Right now there isn't any formal way to deprecate only some specific
elements of an enum. So this is just documented.

You can deprecate all the enum using ATK_DISABLE_DEPRECATED like in
other projects, but if you try to do the same for some specific
elements, you will find problems when you compile the glib-mkenum
generated enum types (unless you want to break the ABI).

https://bugzilla.gnome.org/show_bug.cgi?id=697968
doc: Update atk_text_get_text_{at/before/after}_offset documentation

https://bugzilla.gnome.org/show_bug.cgi?id=697968
Release 2.9.3