audacity: bump to 2.0.5

Note that soundtouch support is needed for changing pitch and tempo.

Also, ffmpeg support is only valid for ffmpeg < 0.11; left in in case someone
wants to install an old version of ffmpeg for this feature.
Upstream bug: http://bugzilla.audacityteam.org/show_bug.cgi?id=540

Change-Id: I93b075d314c273fb857699fd8a996e297fe519ec