bug#31376: 26.0.50; print-charset-text-property not honored

[Eli Zaretskii]

> Date: Fri, 11 May 2018 12:58:11 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: 31376@debbugs.gnu.org, schwab@linux-m68k.org, eller.helmut@gmail.com
> 
> > We should also mention in the doc
> > string that any non-nil, non-t value is treated as 'default'.
> 
> That doesn't sound great - not very conventional.
> Instead of `t' meaning something special and other
> non-nil meaning something non-special we usually
> have a mnemonic symbol for the special case and
> other non-nil for the non-special case. 

Usually, but not always.  We have examples of the other behavior as
well.