* xmpp/rudel-xmpp.el (header): downcased keywords
  (rudel-xmpp-transport-version): new constant; version of the XMPP
  transport backend
  (rudel-xmpp-protocol-version): changed meaning; now XMPP protocol
  version understood by the transport backend
  (rudel-xmpp-backend::initialize-instance): use
  rudel-xmpp-transport-version
  (rudel-xmpp-backend::rudel-make-connection): renamed `rudel-connect'
  -> `rudel-make-connection'
  (rudel-xmpp-state-new): added documentation string
  (rudel-xmpp-state-negotiate-stream::success-state): added
  documentation string
  (rudel-xmpp-state-negotiate-stream): added documentation string
  (rudel-xmpp-state-negotiate-stream::rudel-enter): fixed comment;
  generate stream version from `rudel-xmpp-protocol-version'
  (rudel-transport-set-handler): added documentation string