Add IrcAwayMessage::isReply()
Fix IrcAwayMessage composing (RPL_AWAY != RPL_[UN|NOW]AWAY params)
IrcBufferModel: fix delivery of IrcAwayMessage
Revise auto testing for composed messages
Add IrcAwayMessage::isAway()
Test IrcAwayMessage::reply & ::away
Add new properties to tst_IrcMessage::testAwayMessage()
IrcChannelPrivate::processAwayMessage(): use IrcAwayMessage::isAway()