version 1.6.0

See
http://forums.radioreference.com/digital-voice-decoding-software/256111-
dsd-1-6-closed-fork-open-source.html#post1884783
new options to control filters and P25 encrypted signals

I have added the -l and -pu options.
Merge commit '20271c6df57dacbaed3f2255a8230f44f58bd3ae'

Apparently when 1.6.0 was release it was not properly merged. This re-add the disable p25 encryption muting flag.

Conflicts:
	README
	dsd.h
	dsd_main.c
	dsd_symbol.c
	p25p1_ldu1.c
	p25p1_ldu2.c