[COMMITTED PATCH] Add stub arch-fork.h header.

[Roland McGrath <roland at hack dot frob dot com>]

In fixing the mips/powerpc breakage I failed to realize I was breaking the
other machines that I hadn't yet touched.  This gets back to the status
quo.

Thanks,
Roland


	* sysdeps/unix/sysv/linux/arch-fork.h: New file.

--- /dev/null
+++ b/sysdeps/unix/sysv/linux/arch-fork.h
@@ -0,0 +1,27 @@
+/* ARCH_FORK definition for Linux fork implementation.  Stub version.
+   Copyright (C) 2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This file should define the function-like macro of no arguments
+   ARCH_FORK to an INLINE_SYSCALL invocation of the clone-like system
+   call, passing the CLONE_CHILD_SETTID and CLONE_CHILD_CLEARTID flags
+   and &THREAD_SELF->tid as the TID address.
+
+   Machines that lack an arch-fork.h header file will hit an #error in
+   fork.c; this stub file doesn't contain an #error itself mainly for
+   the transition period of migrating old machine-specific fork.c files
+   to machine-specific arch-fork.h instead.  */