Is `HTML_ABSOLUTE_LINKS` needed? Is it a good idea?

It seems that the `AbsolutePrefix` parameter having the empty string value would not make sense. So, you could use reserve the empty string value to indicate this option is off.

I.e., `options.flags&HTML_ABSOLUTE_LINKS != 0` can be `options.parameters.AbsolutePrefix != ""`.

That would be simpler and eliminates the possibly confusing situation where a user sets `AbsolutePrefix` to some value, but forgets to turn on `HTML_ABSOLUTE_LINKS`, and ends up having the prefix ignored.

Of course, if having an empty string value for `AbsolutePrefix` has another use, then having `HTML_ABSOLUTE_LINKS` is justified.