- make *all* class members start with underscore (not all but two)

- make *all* class members start with underscore (not all but two)
- NEVER EVER use leading underscores for auto variables
- don't store values in auto variables for the next function call (not
  even when they start with underscore :-)   This fixed the TACAN
  channel lookup, which was supposed to be done on channel changes only,
  but was always done)
- only do frequency search if frequency has changed (this was apparently
  planned, but not finished; leftover from adf.cxx?)
- don't use double as bool switch
- some minor cleanup