New cpp0 warning in 3.1 breaks configure (autoconf)

[Jonathan Lennox]

Russ Allbery writes:
> Is there any way to warn about /usr/include without warning about
> /usr/local/include?  Packages that add -I/usr/include are buggy and the
> maintainers need to fix them, whether they realize that or are willing to
> face it or not.  I have no sympathy there.  But -I/usr/local/include is
> less obviously wrong.

Would it be possible to warn explicitly about -I inclusion of directories
that have fixincluded headers?  I think a message such as
     cpp0: warning: directly searching directory /usr/include, which has
           fixincluded headers

would be clearer to people.

Or, alternately, could the preprocessor just automatically translate
-I/usr/include into -IPREFIX/whatever/include -I/usr/include?

-- 
Jonathan Lennox
lennox@cs.columbia.edu