enable bidirectional me with x264

patch by Robert Swain <robert =dot= swain =at= gmail =dot= com>

Originally committed as revision 7422 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/x264.c

@@ -225,6 +225,7 @@ X264_init(AVCodecContext *avctx)
     x4->params.analyse.i_me_range = avctx->me_range;
     x4->params.analyse.i_subpel_refine = avctx->me_subpel_quality;
 
+    x4->params.analyse.b_bidir_me = (avctx->bidir_refine > 0);
     x4->params.analyse.b_bframe_rdo = (avctx->flags2 & CODEC_FLAG2_BRDO);
     x4->params.analyse.b_mixed_references =
         (avctx->flags2 & CODEC_FLAG2_MIXED_REFS);