do not try to get aspect information from source twice in twopass mode, fixes bug reported by DuClare

better fix for ffmpeg ogg decode issue, taken from https://roundup.ffmpeg.org/roundup/ffmpeg/issue1723

 timing resolution, as that's what SRT timings may have.

add patch to revert change to ffmpeg decoder that breaks reading some ogg theora files, https://roundup.ffmpeg.org/roundup/ffmpeg/issue1723

patch to update f2t to output skeleton 3.2. Use 64bit offsets and counts for index, and stores the offset of the first non-header page. patch by cpearce