Bump arduino.mk to fix building without native avr-g++.
Revert "Hack into the PWMs to enable audio output. Value in interrupt handler controls tone."

This reverts commit f59ddbd84a6e272e64996efd03b16374948185b3.
Use ttyUSB* instead of ttyACM*.
Add a test with librtty - not sending anything we can decode.
Compile for chipkit.
Give RTTY library a buffer to work with.
Add status notes.