bring Guidebook.txt up to date

bring Guidebook.txt up to date

I may not get around to doing anything with 'C' vs `C' vs \(oqC\(cq
for a while.  Bring Guidebook.txt up to date now rather than waiting
so that the repository's copy reflects the #H7444 fix.

This has ended up with substantial spurious differences due to it
placing padding in different spots during line justification.  I
hope that's due to different groff version using a slightly different
algorithm rather than something like phase of the moon.  :-]
There also differences caused by "..." taking less space than ``...''.