* qatar/master:
  lavfi: unref AVFilterLink.out_buf in ff_end_frame().
  lavfi: unref AVFilterLink.cur_buf in ff_end_frame().
  vsrc_testsrc: avoid an unnecessary avfilter_ref_buffer().
  vf_slicify: clear AVFilterLink.cur_buf in start_frame().
  vf_settb: simplify start_frame().
  vf_fieldorder: don't give up its own reference to the output buffer.
  vf_pad: don't give up its own reference to the output buffer.
  vf_overlay: don't access a buffer reference that's been given away.
  vf_drawtext: don't give up its own reference to the input buffer.
  vf_gradfun: don't store two pointers to one AVFilterBufferRef.
  vf_delogo: don't store two pointers to one AVFilterBufferRef.
  vf_aspect: clear AVFilterLink.cur_buf in start_frame().
  lavfi: add avfilter_unref_bufferp()

Conflicts:
	doc/APIchanges
	libavfilter/avfilter.h
	libavfilter/buffer.c
	libavfilter/vf_aspect.c
	libavfilter/vf_drawtext.c
	libavfilter/vf_overlay.c
	libavfilter/vf_pad.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>