x11 Bell event handling plug-in

Hi all compiz people.

We Hypra humbly present another of our modest contributions.
We did a bell plug-in, that listens to X11 events, and launches actions accordingly. For now it can handle x11 bell, and play sound.
The main problem solved is that before, one couldn't adjust the system sound levels for events, and this could prove very ear-blasting in situations for blind people, who greatly rely on sound harmony for their access to the desktop.
This is meant to be completed, and to handle more events in time.

As to the sound dependency, we didn't add any, and relied on external system call, this way system's agnosticism is respected, although it might not have a very nice finish.

With this plug-in, the user can set a custom sound for the X11 bell event, and an associated volume. There is also an option to let the desktop handle the events, for example with gnome-canberra.

the attached patch is applicable to current master, and has been tested on ubuntu-mate 15.10
We are of course listening for any request from you, regarding coding style, legal issues, beer drinking, whatever.
--
ksamak
ksamak on freenode/#ubuntu-desktop