[TUHS] Can't break line warning

[Douglas McIlroy]

This may be due to logic similar to that of a classic feature that I
always deemed a bug: troff begins a new page when the current page is
exactly filled, rather than waiting until forced by content that
doesn't fit. If this condition happens at the end of a document, a
spurious blank page results. Worse, if the page header happens to
change just after the exactly filled page, the old heading will be
produced before the new heading is read.

Doug