report with biggest nodes

[Karl Berry]

Patrice -- just a stray thought: how hard would it be to dump out a list
of nodes sorted by the number of lines (or words) they contain?  Just
an auxiliary output kind of like the crazy "internal links" file
(although this could be controlled by a directive, no need for an option).

The idea is to identify the biggest nodes, which are likely to be the
ones most in need of splitting up.  (I got to thinking about this as I
was writing up #line and the description kept getting longer.)  

If it's at all troublesome, don't worry about it.  It's obviously easy
enough to do with a separate utility.  But if it's trivial, I figured it
could be built-in.

Thanks,
karl