Re-orthogonalize the matrix in FlyNav::navUpdate().
Otherwise it'll blow up within a few dozen iterations.

New "-fly" config option, and "fly <buttonpov>,<buttoncenter>,<tspeed>,<rspeed>"
control command.  I don't know which button is which, so it's configurable on the fly.

rather than the CAVE origin.  Use position only -- keep the orientation
of the CAVE.

This still might not be right.  Might be better to put the
target point just behind the head, so an origin crosshair doesn't bug us.

to "parti.NNNN.log" for ProcessID NNNN.

parti.NNNN.log, where NNNN is the SZGClient ProcessID.
Maybe this too should be changed -- should we just try to log
to one big file, to limit clutter?  Every line is already labelled with [PID] now.

Don't use exit(0) in command parser.  Set a shared quit flag instead,
and have everybody (?) exit later.

<string>.append( C_string, len ) never copies in the string's trailing \000,
so add it ourselves.

Only create a listenSocket if we're the master -- avoid races to grab the port.
I'm not sure when is best to determine master-hood, so out of superstition
we do it in the first preExchange callback.

Yes, we *do* need to initialize cmdbuf_ to be *empty*.

szg gets mad if we try to select size 0.

properly earlier and (b) might have been changed by command-line I/O.
I.e. let the "run" command work if included in a .cf file.

Tidy list insert/deletion.
Call clock_tick() periodically in master to allow time to pass.
onPostExchange: Add more error checking.
main: Hack to allow running under Linux+freeglut in standalone mode.

for listening for commands from network;
transfer fields; attempts to get "play" to play, etc.
Some from Stuart: PpCmd uses string object;
passing PpCmd commands by transfer-field
from master to slaves.

according to whether msg() or warn() was called.

onWindowStartGL() returns void.

Implement PpCmd interface for serializing commands for network transport.

though not to process any commands after command-line startup yet.