dsound: use accurate position when getting playposition

This flag is Vista+ only, but gives much better accuracy in
delay calculations
AE: Let sinks provide GetDelay function that timestamps values

This uses accurate timer ticks instead of milliseconds to
reduce unneccessary millisecond jitter at later stages.

For now fallbacks exist to not upgrade sinks directly
d3d: take scanline into account when calculating vblank time

This increases precision from thread scheduling precision, to normally
sub millisecond precision for the video reference clock.
osx: add accurate GetDelay() function using timestamps from osx

This uses a lockless approach to get tick/delay/readsize in sync.
It does so by making sure rendercallback is neither running
nor has run at any point while we are grabbing data. The
render callback is high prio, thus this busy wait loop
should only ever trigger for a very short time.
AE: let timestamps from sink delay propagate as far up as possible
osx: fix video ref clock to use timestamp of display instead of now

Now represent the time of the call, OutputTime represent when this
frame is to be displayed. Thus technically it's the next vblank,
but i don't think it's worth adjusting for.
fixup! osx: add accurate GetDelay() function using timestamps from osx
fixup! osx: add accurate GetDelay() function using timestamps from osx
AE: add generic spin locker for low prio consumers
ios: accurate GetDelay() function
Merge branch 'clocks' of https://github.com/elupus/xbmc into clocks