Put is_mms under ifdef CONFIG_MMSH_PROTOCOL, avoids warning:

libavformat/asf.c:112: warning: 'is_mms' defined but not used

Originally committed as revision 11815 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/asf.c

@@ -108,11 +108,13 @@ static void get_str16(ByteIOContext *pb, char *buf, int buf_size)
 }
 #endif
 
+#ifdef CONFIG_MMSH_PROTOCOL
 static int is_mms(ByteIOContext *pb)
 {
     return url_fileno(pb) && url_fileno(pb)->prot &&
          !strcmp(url_fileno(pb)->prot->name, "mmsh");
 }
+#endif
 
 static void get_str16_nolen(ByteIOContext *pb, int len, char *buf, int buf_size)
 {