finally!!! fix the alsa thing

Finally figured out how to tame alsa-1.0.28's wierd bug (not many seem
to be experiencing it so it must be something idiosyncratic to gcc490 or
somehow specific to my system).  Drops all the old hacks and just
depends on a revbumped alsa-lib ebuild when alsa use-flag is set.

Signed-off-by: Gregory M. Tuner <gmt@be-evil.net>