This change allows the set_mode functions to leave the rig passband
unchanged if required. For the few rigs that do not have explcit
passband width control either current state is read and rewritten or a
"normal" width is chosen e.g. select a normal width when there is a
choice like CW and CW-NARROW.
As Hamlib now restores the rig auto information state (AI) on exit
there is now a need to disable that functionality so that rigctl can
be used to set/reset AI mode on the rig explicitly.
A new public API function 'rig_no_restore_ai()' is also added that
allows any client to disable this auto AI restore functionality if
required. Most clients should do nothing as restoring AI state is a
good thing.
Bill Somerville