Fix handling of GR_USE_SYSTEM_LIBGSM and GR_USE_SYSTEM_LIBCODEC2
blocks: remove stray ctrlport XML definitions
Merge remote-tracking branch 'maitland/gr-vocoder-use-system-codecs' into maint
vocoder: minor cleanup in library detection
digital: fixes a bug in the mpsk SNR estimators where they were reporting 3 dB too high.
support comedi whenever found

Remove the LINUX dependency from the gr-comedi CMake rules,
as, for example, comedi also has support on Debian kFreeBSD
which is not a LINUX platform.
find USB on all platforms

Keep the 'usb-1.0' as the preferred match, but also match simply
'usb' as provided on some platforms. Allows kFreeBSD system support.