SS5: improvements

SS5: improvements
- sending clear forward is now forced at any state
- sending signals are queued until last signal has vanished
- timeout while seized/dialing, as well as after busy/clear back
- release of party clears the line (after timeout)
- several minor features and fixes

it is now possible to break the outgoing exchange with:
 2600+2400 140ms
 0 ms delay
 2400      200ms
manually acknowledgement of the answer signal is required then. therefore
the mute feature must be disabled. the delay feature should be used.