Gnome-settings-daemon suffers from some minor ALSA-related mute issues. Here's a
few cases where this matters:
* I mute using the panel applet, and unmute using the keybindings (it'll remute)
* I mute using the panel applet, and then try to unmute (by upping volume) using
the keybindings (it'll start back from zero)

This patch fixes it by b keeping state, similar to how the panel applet and the
volume control do it. I only looked at the GStreamer backend, since it does all
ALSA craziness internally already.

Also, it links to all backends it finds, so if it finds both gst and alsa and
oss, it'll build/link to all of them, which isn't needed, so this patch fixes
that too. GStreamer is used as default (similar to gnome-media/gnome-applets).

I shortly talked to Jonathan, who told me this was probably a good idea
(although he didn't consider himself maintainer). Jody said something similar.
I'm not sure who maintains this (I think Bastien did work on this at some point,
and I was told Seb is doing maintainance work on this too, so CC'ing them), but
feel free to comment. ;).