Revert r14484 hunk that deleted the 'include avcodec.h' statement.

Originally committed as revision 14495 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/audioconvert.c

@@ -25,6 +25,7 @@
  * @author Michael Niedermayer <michaelni@gmx.at>
  */
 
+#include "avcodec.h"
 #include "audioconvert.h"
 
 typedef struct SampleFmtInfo {