* qatar/master:
  lavfi: add compand audio filter

Conflicts:
	Changelog
	doc/filters.texi
	libavfilter/Makefile
	libavfilter/af_compand.c
	libavfilter/allfilters.c
	libavfilter/version.h

The filter is added as new one so as to ease clean merging of its changes
in debug-able steps
See: 6b68e2a4Merged-by: Michael Niedermayer <michaelni@gmx.at>