#include_next fix for libio

[Zack Weinberg]

On Sun, Apr 02, 2000 at 10:20:15PM -0700, Jason Merrill wrote:
> Why is this necessary?  I missed the relevant cpp changes.

If -Wtraditional is on, #include_next will get a warning.  The warning
is disabled in system headers, but when you're compiling libio, that
wrapper isn't considered a system header.  (See the other thread on
this.)

I just grepped the entire tree for #include_next - if libio isn't
compiled with -Wtraditional, the patch is unnecessary (but harmless).

zw