a) handle cases where RX2 is referred to but only one RX is available

a) handle cases where RX2 is referred to but only one RX is available
b) TX menu: TUNE power setting is now such that one gives a the value of
   the drive slider that should be effective when tuning, so no longer
   a percentage of the current position of the drive slider
c) ClientServer: moved that part of this code that used to be in ext.c
   to client_server.c (where it belongs)
d) Fixed frequency changes while CTUN is active
e) allow for CW with a keyer attached to the radio when LOCALCW is
   not active