dsynth - add 'dsynth monitor' directive

dsynth - add 'dsynth monitor' directive

* Create a statistics monitoring file in LOGS/stats/monitor.dat and a
  lock file in LOGS/stats/monitor.lk that can be used to test whether
  dsynth is running or not.

* Add 'dsynth monitor', a front-end which monitors a dsynth already
  running in the background.  Any number of monitors can be in
  operation and killing the monitor has no effect on the running dsynth.

  If no additional argument is given the directive locates the
  monitor.dat file via the configuration (LOGS/stats/monitor.dat).

  You may specify a specific monitor.dat file if desired but note
  that if you do so logs will not be available and the monitor will
  also not be able to detect if dsynth is not running or when dsynth
  exits.

* Reorganize a few things so we can use the ncurses code for both
  the ncurses display feature and the monitor feature.

* Compartmentalize the log line reading code.