Major Rewrite of SBS output code

Remove dependency of the SBS output code on the historic (a) aircraft
structure. The only items that were required were the decoded aircraft
Lat/Lon and these are now included in the mm structure.

Rewrite the SBS output code to use mm->bFlags when populating the output
fields. This ensures that all available data is output, and also that no
stale data is sent.

Using the mm->bFlags variable for SBS output means there is no further
requirement for the sbsFlags member in the aircraft structure, so remove
it.

Cross your fingers and hope this hasn't introduced too many bugs !