Added class representing M17 callsign objects. Objects can be
constructed both from strings and base-40 encoded values and allow
conversion to any of the other representation. The class implements the
comparison operator to allow easy check for callsign match.
New DC block filter implementation using fixed-point math and guaranteeing
zero DC component on the output signal.
Signed-off-by: Silvano Seva <silseva@fastwebnet.it>
Ryan Turner
Silvano Seva
Alain Carlucci