facebook: jid to username conversion

- lots of cleanup and memory related issues fixed
- libcurl extremely slow to fetch `usernames`, find
  a new solution perhaps `evhttp` ?
src: Enhancements

- Make libcurl pipeline the requests, slight increase id_to_username()
  performance.
- Restructure the previous code and make it more readable
src: id->username buddy messaging working

- add new utils function is_facebook ()
- do_send_message_no_hook() now supports username->id conversion
- tested sending messages its working fine, '/who' is not working yet

TODO: wait prompt till id->username isn't finished
src: Fix spurious buffer overflow issues
src: error check jid_username_id converstion
src: handle presense messages and online buddies
src: add delay for graph.facebook.com