Net::XMPP2 missing functionality to be RFC 3920 conform:
   - improve error handling for SASL to 
     support retries as specified in RFC 3920.
     (eg. by supporting a method sasl_retry() which takes
      the changed credentials)
   - SRV record lookup: weight handling!
   - test Net::XMPP2::Error for bind_error and stream_error.
   later:
      - make dns resolution async!
      - make extensions more optional and reentrant

Net::XMPP2::IM missing functionality to be RFC 3921 conform:
   - message and presence sending (mostly done?)
      - handle subscriptions
   - message and presence receiving
   - 7.2.  Business Rules

objectvies to look out for:
   - add high-level events together with low-level events which just
     pass on the XML nodes.
   - TLS: implemented, just do some extensive testing WRT blocking,
          i don't trust the current way the watchers are handled,
          i'm in fear of deadlocks...