Fix preprocessor/11839

[Geoff Keating]

Neil Booth <neil@daikokuya.co.uk> writes:

> My cppfiles.c rewrite fixed the case where a file was unreadable
> (we wouldn't complain, and continue searching) but missed the
> case where a path component is a file.  I tried to create a
> testcase for this, and failed.

It's unrelated to this patch, but have you considered instead having
an immediate error for the case where a file is unreadable?  Normally
that is due to a broken build environment.  You usually don't want the
compiler going on and perhaps finding another file of that name
somewhere else.

-- 
- Geoffrey Keating <geoffk@geoffk.org>