Merge remote-tracking branch 'qatar/master'

* qatar/master:
  vf_pad: use the name 's' for the pointer to the private context
  vf_overlay: use the name 's' for the pointer to the private context
  vf_lut: use the name 's' for the pointer to the private context

Conflicts:
	libavfilter/vf_lut.c
	libavfilter/vf_overlay.c
	libavfilter/vf_pad.c

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