Use libcanberra to warn for trash empty (at least)

[Luca Ferretti <elle uca libero it>]

Just a quick note.

It seems that libcamberra was approved as external dep for GNOME 2.24.

Moreover, the new Audio capplet (libcanberra enabled) lists a "Empty
Trash" event sound.

Could be interesting actually play this sound when you are going to
empty your trash.

For more info, see freedesktop.org for audio theme/naming spec[1] and
see this (really trivial) change[2] in Epiphany (gnome-2-24).

Cheers, Luca.

[1] 
http://www.freedesktop.org/wiki/Specifications/sound-theme-spec
note there are a lot of useful named sounds for Nautilus, such as
"trash-empty", "item-deleted", "file-trash", "completion-*",
"device-added" "device-removed", "complete-copy", but maybe by now
sounds for those events are not yet provided by any theme

[2]
http://svn.gnome.org/viewvc/epiphany?limit_changes=100&view=revision&revision=8361
http://svn.gnome.org/viewvc/epiphany?limit_changes=100&view=revision&revision=8364