Some further work toward adding more AI/ATC messages. This patch provides

Some further work toward adding more AI/ATC messages. This patch provides
some prepratory work for assigning different operations to different
frequencies. It also returns a stub for returning an ATIS message ID.
Currently, the ATIC information ID is hardcoded to "Sierra", which needs
to be replaced by a dynamic ID once ATIS services are fully integrated
with the new trafficcontrol code. At least, it's marginally more realistic
then the previous information XX. :-).