Travis-CI: Report new nightly build site in IRC notification.

Merge branch 'travis_modernize'

CPLD: Update 20150901 bitstream due to Makefile changes.

Not sure if any changes have actual significance, but...

Touch: Adjust thresholds and parameters for new scan.

Quiet narrowing conversion warning.

Remove FSK from receiver menu. It doesn't do anything (yet).

Simplify audio muting.

Zero out the audio buffer instead of muting the codec. The HPF (and other downstream signal processing) can continue running, not produce discontinuities from being effectively halted during mute.