Format characters include the white space after tokens,
which doesn't show up with bold, etc., but is still wrong.

There is additional white-space inserted after a format change is
followed by a numeric HTML entity. This _does_ show up, and it looks
ugly. It's a format that's rarely used, but really needs fixing. 
Unfortunately, this will require a radical change to the formatting
logic's finite-state machine, and is risky. I'm reluctant to fix this
before the next major revision.

Metadata could be handled more elegantly; not all attributes
are shown at all.

Output single HTML document?

Refactor wstring memory management, so that appending a single
character is faster.
