This program listens for sound. If it detects any, it starts recording
automatically and also automatically stops when things become silent again.

Listener requires portaudio.

In order to use this, a few steps need to be completed first:

1. Run setlistener (as an ordinary user), and use the
   cursor keys on your keybord to move the "|" left and right until
   <silence> appears in place of <SOUND!>. Make a note of the "Current
   detection level", and modify the detect_level value in
   /etc/listener.conf to match.

2. To start, run listener -f (to prevent it forking to the background.
   Omit -f if you wish to fork). Output will be saved in the current
   directory as an ogg file by default.