lavu/log: do not skip overwritten lines.

If the line ends with \r, it will not flood the tty, and
the "Last message repeated" line would overwrite it.
Fix bug introduced by c25d1ba.
ffmpeg: remove obsolete workaround in trim insertion.

The bug it was working seems to have been fixed.
This change causes ffmpeg to use the trim filter to implement
the -t option.
FATE tests are updated due to the more accurate handling of
the last packets.
Merge remote-tracking branch 'cigaes/master'

* cigaes/master:
  ffmpeg: remove obsolete workaround in trim insertion.
  lavu/log: do not skip overwritten lines.

Merged-by: Michael Niedermayer <michaelni@gmx.at>