avstring: Mark some character handling functions av_const

Signed-off-by: Martin Storsjö <martin@martin.st>
lavf: Add an option for avoiding negative timestamps

This is the same logic as is invoked on AVFMT_TS_NEGATIVE,
but which can be enabled manually, or can be enabled
in muxers which only need it in certain conditions.

Also allow using the same mechanism to force streams to start
at 0.

Signed-off-by: Martin Storsjö <martin@martin.st>
lavf: Print a warning if failed to avoid negative timestamps when requested

Signed-off-by: Martin Storsjö <martin@martin.st>
Merge commit '4981baf9b803f3c4866b2e97fdadb008c62dc7ad'

* commit '4981baf9b803f3c4866b2e97fdadb008c62dc7ad':
  avstring: Mark some character handling functions av_const

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '1384df641994bf3d6cb51084290aa94752737bae'

* commit '1384df641994bf3d6cb51084290aa94752737bae':
  lavf: Add an option for avoiding negative timestamps

Conflicts:
	libavformat/avformat.h
	libavformat/mux.c
	libavformat/options_table.h
	libavformat/version.h

See: 3ba0dab76ac32f0c9f50c916a73bc64e43c1fdf9
See: a89c01253190b9eb9de8e28a3252423bf7732511
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '897d5c3a4296f3da80b8699d1487328ca2de8e55'

* commit '897d5c3a4296f3da80b8699d1487328ca2de8e55':
  lavf: Print a warning if failed to avoid negative timestamps when requested

Conflicts:
	libavformat/mux.c

See: ec6a5fc6cca22e4eb0a91cc8fba786d41ade2032
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Support raw dvdsub palette as stored on normal dvd's

This is how the palette is stored on dvd's. Currently
only xbmc passes the palette information to libavcodec
this way.
Check return value of avio_seek and avoid modifying state if it fails

The code still modifies state if the timestamp is not found. Not
sure exactly how to avoid that.
asf hacks
if av_read_packet returns AVERROR_IO, we are done. ffmpeg's codecs might or might not handle returning any completed demuxed packets correctly
added: Ticket #7187, TV Teletext support for DVB EBU Teletext streams
Don't accept mpegts PMT that isn't current
Don't reparse PMT unless it's version has changed
Read PID timestamps as well as PCR timestamps to find location in mpegts stream
Get stream durations using read_timestamp
changed: allow 4 second skew between streams in mov before attempting to seek
fixed: memleak in mpegts demuxer on some malformed (??) mpegts files with too large pes packets

at-visions sample file brokenStream.mpg
Speed up mpegts av_find_stream_info
dxva-h264 Fix dxva playback of streams that don't start with an I-Frame.
add public version of ff_read_frame_flush

We need this since we sometimes seek on the
input stream behind ffmpeg's back. After this
all data need to be flushed completely.