h264 packetizer : correctly compute picture height in case of interlaced video.

See frame_mbs_only_flag chapter 7.4.2.1
(cherry picked from commit 3963704b)

modules/packetizer/h264.c

@@ -901,6 +901,7 @@ static void PutSPS( decoder_t *p_dec, block_t *p_frag )
 
     /* b_frame_mbs_only */
     p_sys->b_frame_mbs_only = bs_read( &s, 1 );
+    p_dec->fmt_out.video.i_height *=  ( 2 - p_sys->b_frame_mbs_only );
     if( p_sys->b_frame_mbs_only == 0 )
     {
         bs_skip( &s, 1 );