unnecessary warning in gcc-2.96

[Martin v. Loewis]

> IMO, compiler shouldn't care for the contents of a commented area, but
> I could be wrong.

The problem is that trigraphs are processed *before* comments are
detected, so the processing of trigraphs might influence what a
comment is.

Nevertheless, there is a plan to not emit the warning if it can be
determined that interpreting the trigraph would not change the meaning
of the program.

Regards,
Martin