asfdec: don't strip the "WM/" prefix, this should be done during conversion.

Patch by Anton Khirnov wyskas gmail com

Originally committed as revision 22057 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/asfdec.c

@@ -175,8 +175,6 @@ static void get_tag(AVFormatContext *s, const char *key, int type, int len)
         av_log(s, AV_LOG_DEBUG, "Unsupported value type %d in tag %s.\n", type, key);
         return;
     }
-    if (!strncmp(key, "WM/", 3))
-        key += 3;
     av_metadata_set2(&s->metadata, key, value, 0);
     av_freep(&value);
 }