[gpm] Gstreamer usage

[Jani Monoses <jani monoses gmail com>]

Hello,

these two old bug reports lead to introducing gst as a dependency for beeping in case of critical temperature.

They however do not clarify why the out-of process call of gst-launch and
if that's not available a fallback to the PC speaker would not be good enough.

I know this is an older topic, first being discussed on gnome-devel last october
but I have just seen it, and find it weird to need to depend on gst and have quite a few lines of code just to beep :)

https://bugs.launchpad.net/ubuntu/+source/gnome-power-manager/+bug/82753
http://bugzilla.gnome.org/show_bug.cgi?id=365700#c11

Jani