/dev/mixer is held open by mixer_applet2, prevents sleep

To get my laptop to wake up from sleep, I must unload the sound drivers. To do
that, no processes may use /dev/mixer or any files in /dev/snd. There is a
related bug in capplets, where gnome-settings-daemon is holding /dev/mixer open.
I have not reported this in Ubuntu, because it is fixed in Debian Unstable,
where I reported the bug #255793. Actually, the fix has not yet propagated to
Unstable, since capplets-1:2.6.1-13 has the bug, but capplets-1:2.6.1-14 fixed
it. Arnaud Patard, arnaud.patard/SPAM/rtp-net.org, made the fix that I used.

$ ps axw | grep mixer
 7902 ? S 0:00 /usr/lib/gnome-applets/mixer_applet2
--oaf-activate-iid=OAFIID:GNOME_MixerApplet_Factory --oaf-ior-fd=56

$ lsof /dev/mixer
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
gnome-set 6575 kasper 31u CHR 14,0 5945 /dev/mixer
mixer_app 7902 kasper 34u CHR 14,0 5945 /dev/mixer

$ lsmod | grep snd
snd_intel8x0m 18632 2
snd_intel8x0 33068 3
snd_ac97_codec 59268 2 snd_intel8x0m,snd_intel8x0
snd_pcm_oss 48168 0
snd_mixer_oss 16640 4 snd_pcm_oss
snd_pcm 85540 3 snd_intel8x0m,snd_intel8x0,snd_pcm_oss
snd_timer 23172 1 snd_pcm
snd_page_alloc 11144 3 snd_intel8x0m,snd_intel8x0,snd_pcm
gameport 4736 1 snd_intel8x0
snd_mpu401_uart 7296 1 snd_intel8x0
snd_rawmidi 23232 1 snd_mpu401_uart
snd_seq_device 7944 1 snd_rawmidi
snd 50660 14
snd_intel8x0m,snd_intel8x0,snd_ac97_codec,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_timer,snd_mpu401_uart,snd_rawmidi,snd_seq_device
soundcore 9824 4 snd