compat.h: whitespace cleanup

No functional changes. Just whitespace cleanup

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
compat: add backward support for snd_pcm_stop_xrun

If this function doesn't exist, emulate it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
some fixes for the backward-compat check for snd_pcm_stop_xrun

Committed last patch too early. There are a few bugs on it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>