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
0005-if-av_read_packet-returns-AVERROR_IO-we-are-done.-ff
0006-added-Ticket-7187-TV-Teletext-support-for-DVB-EBU-Te
Don't accept mpegts PMT that isn't current
Don't reparse PMT unless it's version has changed
0010-Read-PID-timestamps-as-well-as-PCR-timestamps-to-fin
0011-Get-stream-durations-using-read_timestamp
0013-aacenc-add-recognized-profiles-array
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.
0024-add-public-version-of-ff_read_frame_flush
ffmpeg 1.2 - fixed dvd still frames ended up in internal lavf