various changes to the documentation, and redefinition of

ao2_hash_fn and ao2_callback_fn typedefs, in preparation
to more cleanup of the _search_flags

Please do not merge this change to 1.4 yet - there are no
functional changes anyways.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@81712 65c4cc65-6c06-0410-ace0-fbb531ad65f3