Deprecate external use of libio.h and _G_config.h.

libio.h was originally the header for a set of supported GNU
extensions, but they have not been maintained as such in many years,
they are now standing in the way of improvements to stdio, and we
don't think there are any remaining external users.  _G_config.h was
never intended for public use, but predates the bits convention.
Move both of these headers into the bits directory and provide stubs
at top level which issue deprecation warnings.

The contents of (bits/)libio.h and (bits/)_G_config.h are still
exposed to external software via stdio.h; changing that requires more
complex surgery than I have time to attempt right now.

	* libio/libio.h, libio/_G_config.h: New stub headers which issue a
	deprecation warning and then include <bits/libio.h>, <bits/_G_config.h>
	respectively.
	* libio/libio.h: Rename the original version of this file to
	libio/bits/libio.h.  Error out if not included by stdio.h or the
	stub libio.h.
	* include/libio.h: Move to include/bits.  Forward to libio/bits/libio.h.
	* sysdeps/generic/_G_config.h: Move to top-level bits/.  Error out
	if not included by bits/libio.h or the stub _G_config.h.
	* sysdeps/unix/sysv/linux/_G_config.h: Move to
	sysdeps/unix/sysv/linux/bits.  Error out if not included by
	bits/libio.h or the stub _G_config.h.
	* libio/stdio.h: Include bits/libio.h, not libio.h.
	* libio/Makefile: Install bits/libio.h and bits/_G_config.h as
	well as libio.h and _G_config.h.

	* csu/init.c, libio/fmemopen.c, libio/iolibio.h, libio/oldfmemopen.c
	* libio/strfile.h, stdio-common/vfscanf.c
	* sysdeps/pthread/flockfile.c, sysdeps/pthread/funlockfile.c
	Include stdio.h, not _G_config.h nor libio.h.
	* libio/iofgetpos.c: Also rename fgetpos64 out of the way.
	* libio/iofsetpos.c: Also rename fsetpos64 out of the way.

	* scripts/check-installed-headers.sh: Skip libio.h and _G_config.h.

1 files changed, 11 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 2a1a4bfd85..95f368340b 100644
--- a/NEWS
+++ b/NEWS
@@ -110,6 +110,17 @@ Deprecated and removed features, and other changes affecting compatibility:
 
 * The tilepro-*-linux-gnu configuration is no longer supported.
 
+* The nonstandard header files <libio.h> and <_G_config.h> are deprecated
+  and will be removed in a future release.  Software that is still using
+  either header should be updated to use standard <stdio.h> interfaces
+  instead.
+
+  libio.h was originally the header for a set of supported GNU extensions,
+  but they have not been maintained as such in many years, they are now
+  standing in the way of improvements to stdio, and we don't think there are
+  any remaining external users.  _G_config.h was never intended for public
+  use, but predates the bits convention.
+
 Changes to build and runtime requirements:
 
 * bison version 2.7 or later is required to generate code in the 'intl'