Also, fix it.

The current workflow is often parsing a subtitle format, then convert it
in a common HTML and then push it to the renderer as HTML. The renderer
will reparse the HTML and try to render it. Of course, that means that
only one renderer can do that correctly, and so we bloat the freetype
renderer as much as we can.
It also means that we have 2 render callbacks for subtitles, one for
normal text and one for styled text, and we sometimes reparse the HTML
to remove the tags, for the first.

We now only use a text_segment, with new segments at every style change;
an unique render function and the renderer can decide to honor or not
the style.

It's a big commit, so regressions can arise, but it was tested for most
common cases.

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

SPS and PPS NAL units always start with 0x00000001 and finish with 0x000000,
0x000001 or the end of the bytestream.

This function returns true if channel extraction is needed.

If layouts are the same, channel extraction should be needed only if the number
of channels is different.

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>