[MPlayer-dev-eng] ao_alsa mixer channel selection

[Reimar Döffinger]

Hi,
> this patch makes alsa aos use the standard -mixer and -mixer-channel 
> options for setting the mixer, instead of its special and undocumented 
> form of -mixer device/channel.
> Manpage patch included.

the part for ao_alsa.c was commited by joyping, the manpage part by me. 
ao_alsa9.c and ao_alsa1x.c were not changed.

Greetings,
Reimar Döffinger