gstaudiobasesink: Refactor alignment computation for clarity
audio/video: Initialize all {audio|video}info fields

Fixes "Unitialized Scalar Variable" issues reported by Coverity.

Has the added advantage of detecting whether somebody *does* use those
fields (ending up with a invalid address).

https://bugzilla.gnome.org/show_bug.cgi?id=720810
gstaudiobasesink: Cosmetics, grammar/spelling

- Drop repeated 'yet' from debug msg
- Drop repeated 'to' from param desc
- Some spelling
gstaudiobasesink: Break some too long lines
gstaudiobasesink: Drop dead _sink_async_play() code
gstaudiobasesink: Factor out reset sync routine
gstaudiobasesink: Retarget FIXME to 2.0

Properly fixing this one would break API
gstaudiobasesink: Always reset avg_skew on _reset

Only case in which it wasn't (READY to PAUSED) should
have had this value reseted too.
gstaudiobasesink: Reset last_align to 0, not -1

This is the expected behavior in READY -> PAUSED
gstaudiobasesink: Always reset last_align

Should be done for all the reset_sync() cases. Not
only for the READY to PAUSED one.