add --version option that works something like this:

add --version option that works something like this:

  $ fgfs --version
  2.0pre-20080314
  FG_ROOT=/usr/local/share/FlightGear
  FG_HOME=/home/foo/.fgfs

... assuming that VERSION in config.h is "2.0pre-20080314". Which it isn't.
Instead it's "1.0.0" since yesterday, and was "0.9.10" before that. This
has yet to be discussed, and I'll add the option to options.xml later.