avformat demux needs -lavcodec (av_free_packet)

(cherry picked from commit b35dc178d7d159a850ace7baec714c5759e40908)

Conflicts:

	configure.ac

configure.ac

@@ -2778,7 +2778,7 @@ AC_ARG_ENABLE(avformat,
 ])
 if test "${enable_avformat}" != "no"
 then
-  PKG_CHECK_MODULES(AVFORMAT,[libavformat libavutil],
+  PKG_CHECK_MODULES(AVFORMAT,[libavformat libavcodec libavutil],
     [
       VLC_SAVE_FLAGS
       CPPFLAGS="${CPPFLAGS} ${AVFORMAT_CFLAGS}"