ffmpeg: release the reader context on destruction.

* avformat_open_input() is to be balanced with a avformat_close_input().
* should help with #9945.
HaikuDepot: ParagraphLayout: Fix work around

 * Bail early if the TextSpan length is 0.
 * When the span starts with a space, the work
   around for the app_server bug, which I should fix,
   needs to offset by the other delta.
HaikuDepot: Paragraph: Added IsEmpty().
HaikuDepot: Added very simplistic markup parser.

 * Follows MediaWiki or TracWiki style.
 * Supports only level 2 headings, bold, italic and top-level
   bullet paragraphs.
 * Line break handling would need to be changed.
 * Outputs a TextDocument.
HaikuDepot: MarkupParser: Fixed off-by-one error...

 ... when finishing a paragraph to include the last character.