alsasink: pause/resume

Submitted by Axel Mårtensson

Created attachment 372823
alsasink: pause/resume

alsasink have no possibility to distinguish between a pause and stop.

This patch adds the functionality to pause, stop and resume for the alsasink.

Pause and resume takes use of snd_pcm_pause() to handle the pause/resume capabilities.

The following patch is required to expose the pause, resume and stop vmethod to alsasink: https://bugzilla.gnome.org/show_bug.cgi?id=788361

~~Patch 372823~~, "alsasink: pause/resume":
0003-alsasink-pause-resume.patch