x264: use x264_picture_init() from X264_BUILD >= 98

(cherry picked from commit aa34b13d)
Signed-off-by: Ilkka Ollakka <ileoo@videolan.org>

modules/codec/x264.c

@@ -1306,7 +1306,11 @@ static block_t *Encode( encoder_t *p_enc, picture_t *p_pict )
     int i_nal, i_out, i;
 
     /* init pic */
+#if X264_BUILD >= 98
+    x264_picture_init( &pic );
+#else
     memset( &pic, 0, sizeof( x264_picture_t ) );
+#endif
     pic.i_pts = p_pict->date;
     pic.img.i_csp = X264_CSP_I420;
     pic.img.i_plane = p_pict->i_planes;