Merge remote-tracking branch 'qatar/master'

* 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>

libavfilter/vf_transpose.c

@@ -189,10 +189,8 @@ static void end_frame(AVFilterLink *inlink)
         }
     }
 
-    avfilter_unref_buffer(inpic);
     ff_draw_slice(outlink, 0, outpic->video->h, 1);
     ff_end_frame(outlink);
-    avfilter_unref_buffer(outpic);
 }
 
 static void null_draw_slice(AVFilterLink *link, int y, int h, int slice_dir) { }