If maxMsgs is not set, the message is added to the queue and the
owner is notified. If the queue is full, the message will still be
accepted if it is a control message, otherwise onCrowdingDoThis is
called. If the routine returns true, this call will block until
the owner has made space available in the queue. If it returns
false, this call will abort.
Add a message that will trigger in the future.
If maxMsgs is not set, the message is added to the queue and the owner is notified. If the queue is full, the message will still be accepted if it is a control message, otherwise onCrowdingDoThis is called. If the routine returns true, this call will block until the owner has made space available in the queue. If it returns false, this call will abort.