Add missing #include.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@26127 b3059339-0415-0410-9bf9-f77b7e298cf2

command.c

@@ -61,6 +61,7 @@
 
 #include "mp_core.h"
 #include "mp_fifo.h"
+#include "libavutil/avstring.h"
 
 #define ROUND(x) ((int)((x)<0 ? (x)-0.5 : (x)+0.5))