Rebuild doc/*.txt (other than Guidebook) with 'nroff -man -c -Tascii'
rather than just 'nroff -man' to prevent it generating non-ASCII
characters for hyphen, aprostrophe, single and double quotes, long
dash, possibly others. Also preprocess with '--grep-define ALLDOCS'
so that a few parts of the text don't end up being specific to the
local configuration.
The next time they're rebuilt they'll probably be subject to the
ping-pong effect of inserting padding spaces for justification
(alternating right-to-left vs left-to-right as intended but starting
with different parity so lots of gratuitous changes) since my quite
old version of groff triggers that for Guidebook.txt.
