[Groff] antiquity of troff

[Doug McIlroy]

> troff pre-dates C by quite a while

Actually not.  C and nroff were contemporary--both debuted in 2nd edition Unix.
troff came in the 3rd edition.  Of course nroff was preceded by roff, and
that by runoff; but neither of those had a | operator, which was the
triggering question.  Certainly by the time | for absolute page coordinates
appeared in nroff/troff, C was well known to all involved.

roff, the original of which I wrote, did not have expressions, though
it did support constructions like .ps +2 to increment and decrement
parameters.