Patch for building with latest FFmpeg 3.0
https://bugs.gentoo.org/show_bug.cgi?id=575328

Inspired by
https://raw.githubusercontent.com/Homebrew/patches/1282e60/moc/moc-2.5.0.diff

We can unconditionally depend on the existence of 'channel_layout.h',
as even the oldest version in the Gentoo tree contains this header.

--- moc-2.6-alpha1/decoder_plugins/ffmpeg/ffmpeg.c
+++ moc-2.6-alpha1/decoder_plugins/ffmpeg/ffmpeg.c
@@ -66,7 +66,7 @@
 GCC_DIAG_ON(deprecated-declarations)
 #include <libavutil/mathematics.h>
 #ifdef HAVE_AV_GET_CHANNEL_LAYOUT_NB_CHANNELS
-#include <libavutil/audioconvert.h>
+#include <libavutil/channel_layout.h>
 #endif
 
 /* FFmpeg also likes common names, without that, our common.h and log.h