The qsy() function will now change the rig frequency when it notices
that the modem is permanently frequency-locked (e.g., MT-63).
* Remove modem_frequency argument and associated code from the various
rig control set_qsy functions, this is now done by qsy().
* Make modem::set_freq() virtual and override it in mt63 in order to
better prevent frequency changes.
* Use qsy() in the RSID decoder and notifier "Go to freq" callback.
Removed duplicate invocations of init() for several
modem types.
Carrier callback
Corrected frequency limits computation in waterfall::opmode()
method.
1. MT63 tx buffer was not correctly initialized at the start
of each transmission.
2. Added Rx Integration length selector to MT63 configuration.
3. Added lowest / highest preamble tones as a signal acquisition
aid. User can enable lowest, both or none.