libavfilter/decimate: Add pts of first frame to all frames.

Fixes ticket #3019

Reviewed-by: Clément Bœsch
build: Ensure that strip commands are run silently
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  build: Ensure that strip commands are run silently

Conflicts:
	Makefile

Not merged as it conflicts with strip being on the BRIEF list

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge remote-tracking branch 'cehoyos/master'

* cehoyos/master:
  libavfilter/decimate: Add pts of first frame to all frames.

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