pulse: Add a wallclock option to be compatible with other other captures

alsa and x11grab use av_gettime() to report timestamps.

Bug-Id: 647
Merge commit '424b929b5cb9ca4094099f25179829260d4b0fa3'

* commit '424b929b5cb9ca4094099f25179829260d4b0fa3':
  pulse: Add a wallclock option to be compatible with other other captures

Conflicts:
	libavdevice/pulse_audio_dec.c

wallclock mode was supported and default in FFmpeg already before this commit.
its thus left the default

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/utils: add GBRP16 to avcodec_align_dimensions2()

Fixes Ticket3869

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>