[AC21.5] Improve comments in faces.c

[Stephen J. Turnbull]

Aidan Kehoe writes:

 >  > +       #### This is questionable.  The problem is that unusual scripts
 >  > +       will typically fallback to the hard-coded values as the user is
 >  > +       unlikely to have specified them herself, a common complaint. */

 > Those users who prefer blank squares in the specified font to a
 > glyph communicating the intended character (however badly) in a
 > fallback font, are idiots.

All I'm suggesting is that a lot of users seem to prefer that there be
as few fallback fonts as possible.  They would prefer a single more or
less consistent font rather than a a collage of styles for different
scripts.