[tex-eplain] \leavevmode in front of hyperlinks

[Karl Berry]

    IOW, I think Knuth-style strict backward-compatibility should be sacrificed

I'm not sure I agree with that principle.

But in this case, I guess it's ok to always do the \leavevmode.  The
commands are of no particular value in vertical mode anyway, and we
certainly don't want users to have to enter hmode explicitly.

      \hlstart{}{}{LABEL}
      Text of the link\hlend.

    When \hloff (and therefore no \leavevmode) there will be no
    space before `Text'; 

I don't understand this example, though.  What does \leavevmode have to
do with whether there is a space or not?  Should \hlstart end with
\ignorespaces?  (Sorry, maybe it'd be obvious if I looked at the code,
but I still haven't. :)

Thanks,
k