Add av_unused to conditionally used variable, fixes the warning:

h264.c:6464: warning: unused variable 'dir'

Originally committed as revision 16925 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h264.c

@@ -6461,7 +6461,7 @@ static void filter_mb( H264Context *h, int mb_x, int mb_y, uint8_t *img_y, uint8
     const int mb_type = s->current_picture.mb_type[mb_xy];
     const int mvy_limit = IS_INTERLACED(mb_type) ? 2 : 4;
     int first_vertical_edge_done = 0;
-    int dir;
+    av_unused int dir;
 
     //for sufficiently low qp, filtering wouldn't do anything
     //this is a conservative estimate: could also check beta_offset and more accurate chroma_qp