For Qt, always render text windows with fixed width font instead
of switching from proportional to fixed when the text contains
any line(s) with four consecutive spaces. That was really meant
for menu lines without selector letters which want to be lined
up under or over ones with such, and wasn't a very good heuristic
for text windows.
Most of the text files for the '?' command happen to have such
lines so are already being shown with fixed-width font. data.base
entries were hit or miss; most have attribution lines indented by
four or more spaces but some don't, so display was inconsistent:
some were shown with fixed-width font and some with proportional.
4445e06d1c