Externally: added a chronometer and a control-position indicator a la
MSFS, along with dummies for the radio-nav gauges.
Internally, substantially reworked the code so that the individual gauges
can be table- (and eventually, file-) driven.
I've reorganized the code in panel.cxx and panel.hxx so that it will
be a little easier to extend the panel later if someone wants to.
It's still basically Friedemann's code at the core, but I've
repackaged it into a saner class hierarchy and encapsulated as much as
I could (there are still a couple of circular dependencies that need
swatting). If someone wants to modify it to use SSG or to add new
gauges, it should be a lot easier now.
There are no user-visible changes.
