trigraphs in X3J11

[Henry Spencer]

> I countersuggest that the compiler should always recognize trigraphs, and
> issue a warning message if any are encountered.  Then add an option to supress
> this warning.

Actually, in the experimental scanner I'm playing with, they are always
recognized, but how they are interpreted depends on an option.  If the
trigraph option is on, they are interpreted as per X3J11.  If the option
is off -- the default -- a warning message is produced and each trigraph
is interpreted as three characters.