character references, trailing ';', urls

I was looking at how badly dillo handles something like:

<a href="http://www.dillo.org?asdf&copy=3&micro=zxcv">link</a>

It becomes a much more common problem with html5, which has a
_lot_ more character references.


I could perhaps stick an argument on the Html_parse_entity() in
Html_get_attr2(), telling it to insist upon finding a ';'.

If we still had cvs.auriga, I could dig through prehistory and
try to see whether not demanding ';' termination was initially
done with the strong belief that it was for the best overall
(or maybe it was even inherited from gzilla), but we don't have
cvs.auriga, and we don't have mailing list search working (not
that that's generally very fun to dig through in any case).
After all, maybe we should always insist upon proper termination.