Hi Guix!

Trying to play with sway, I noticed a crash in pavucontrol, when
changing the volume of outputs (strangely enough, not of individual
applications).  This was already reported upstream, and they found the
cause to be the assumption libcanberra makes that you're running on
Xorg.  This commit adds a patch that remove this assumption, and was
pushed to libcanberra after the latest release (in 2012!).