rtpenc_chain: Don't copy the time base to the source stream by default

Only copy it manually in the muxers where it makes sense (rtspenc,
sapenc). Don't touch the original AVStream in movenchint, where
the original AVStream should be kept untouched.

This fixes the normal tracks in RTP hinted files after
abb810db - the hint tracks were ok while the normal media tracks
were broken, noticed by Michael Niedermayer.

This reverts abb810db but achieves the same effect for the other
muxers.

Signed-off-by: Martin Storsjö <martin@martin.st>
Merge commit 'f797b134cad4d248b1c8955659997980d0668bc3'

* commit 'f797b134cad4d248b1c8955659997980d0668bc3':
  rtpenc_chain: Don't copy the time base to the source stream by default

See: 1fe40e1b0538a8eb8425123c47775b5d141ae084
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Revert "avformat/movenchint: Fix movhinting with ff_rtp_chain_mux_open() from abb810db036628e11a5171134ebe320b187ee6d6"

This has become unneeded due to f797b134cad4d248b1c8955659997980d0668bc3

This reverts commit 1fe40e1b0538a8eb8425123c47775b5d141ae084.
libavformat: output cues for each subtitle block in MKV muxer

Signed-off-by: John Peebles <johnpeeb@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>