Add general code to separate the HTML-like attribute=value syntax used
in srt font tags into attribute and value parts. This simplifies some
of the parsing code, makes detection of malformed input more robust,
and allows warning about unrecognized attributes.
Previously the code converting text subtitles to ASS format converted
newline characters, and only those, to ASS "new line" markup. If the
subtitles contained "\r\n", the "\r" was thus left in the text. In
previous libass versions the "\r" was not visible, but in the current
one it produces an empty box. Improve the conversion to remove the
"\r" in that case. Also treat a lone "\r" as a newline.
SubRip subtitles have no "official" spec for any styling support, but
various tags are in common use; previous code filtered out text
between <> to remove HTML-style tags. Add support for those tags and
for MicroDVD subtitle styling. The style display is implemented by
converting the subtitles to the ASS subtitle format and displaying
them with libass, so libass needs to be enabled.
Original patch by Clément Bœsch <ubitux@gmail.com>.
