Add support for media-libs/alsa-lib (Advanced Linux Sound Architecture)

Packages describing “alsa” as local USE flag

Package“alsa” Flag Description
app-emulation/qemuEnable alsa output for sound emulation
games-fps/serioussamEnable support ALSA sound.
media-libs/libcanberraEnables ALSA sound driver.
media-sound/denemoEnable alsa support through media-libs/alsa-lib
media-sound/xwaxAdds support for ALSA audio input/output.
media-tv/mythtvAllows MythTV to directly output sound to ALSA devices
www-client/firefox-binWhen pulseaudio isn't set, this prefers apulse
x11-misc/xmobarUse alsa-mixer to get the volume from soundcards.

All packages providing a “alsa” USE flag (134)