rtpenc_chain: also copy AVFMT_FLAG_BITEXACT to new AVFormatContext

Otherwise it is impossible to make '-movflags +rtphint' bitexact after
FF_API_LAVF_BITEXACT has been disabled.
Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

libavformat/rtpenc_chain.c

@@ -58,7 +58,7 @@ int ff_rtp_chain_mux_open(AVFormatContext **out, AVFormatContext *s,
     rtpctx->max_delay = s->max_delay;
     /* Copy other stream parameters. */
     rtpctx->streams[0]->sample_aspect_ratio = st->sample_aspect_ratio;
-    rtpctx->flags |= s->flags & AVFMT_FLAG_MP4A_LATM;
+    rtpctx->flags |= s->flags & (AVFMT_FLAG_MP4A_LATM | AVFMT_FLAG_BITEXACT);
 
     /* Get the payload type from the codec */
     if (st->id < RTP_PT_PRIVATE)