Checkend out mod_offline_odbc.erl from ea2bc589a0a434.
Deleted webadmin support from mod_offline.
Fully moved from strings to binaries in mod_offline.
Moved backend-specific functions from mod_offline into mod_offline_mnesia.
Added mod_offline.hrl
Added Host argument for all API functions in mod_offline.
Added offline_message MySQL table. Converted mod_offline_odbc into backend.
Removed mod_offline_mnesia:update_table().
Added mod_offline_odbc_legacy.erl
Replaced mod_offline worker with gen_server and put it under supervision.
Add offline_message table definition for PgSQL
Merge branch 'arc-mod-offline-unification' of https://github.com/arcusfelis/ejabberd into arcusfelis-arc-mod-offline-unification

Conflicts:
	apps/ejabberd/src/mod_offline.erl