Now and then, I come across a package which uses configure to test for
the presence/usability of a certain header file, yet mysteriously does
not use the definition in config.h in the source itself.

For instance, X.org's pixman library tests for inttypes.h, but in
pixman.h, they only include it if __OpenBSD__ is defined.

Are there cases where this is the right thing to do?  Not using
HAVE_INTTYPES_H when configure tests for it seems so peculiar to me I
can't help but suspect I'm missing something.

--Blair