Use gnulib-tool to create gnulib source files.

* Add gnulib files generated by gnulib-tool in build-aux, m4 and
    grub-core/gnulib directories
    * .bzignore: Add **/.deps and autogenerated gnulib files
    * configure.ac: Assign auxiliary directory to build-aux, add invocation
    of gnulib macros, add grub-core/gnulib/Makefile
    * Makefile.am: Add gnulib directory in SUBDIRS (removing unnecessary .),
    include m4 directory to aclocal.
    * Makefile.util.def: Remove direct compilation of gnulib source files
    and use the new grub-core/gnulib/libgnu.a.
    * build-aux/config.rpath: move config.rpath from top directory to
    build-aux
    * conf/Makefile.common: Remove the macro _GL_UNUSED already defined
    in gnulib headers
    * conf/Makefile.extra-dist: Add m4/gnulib-cache.m4
    * grub-core/Makefile.core.def: Remove unnecessary extra_dist
    * grub-core/lib/posix_wrap/localcharset.h (locale_charset): Update
    header.
    * grub-core/lib/posix_wrap/langinfo.h (nl_langinfo): Return static
    string.

grub-core/gnulib/sys_wait.in.h

@@ -0,0 +1,106 @@
+/* A POSIX-like <sys/wait.h>.
+   Copyright (C) 2001-2003, 2005-2010 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+
+#ifndef _GL_SYS_WAIT_H
+
+#if __GNUC__ >= 3
+@PRAGMA_SYSTEM_HEADER@
+#endif
+
+/* The include_next requires a split double-inclusion guard.  */
+#if !((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__)
+# @INCLUDE_NEXT@ @NEXT_SYS_WAIT_H@
+#endif
+
+#ifndef _GL_SYS_WAIT_H
+#define _GL_SYS_WAIT_H
+
+#if !((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__)
+/* Unix API.  */
+
+/* The following macros apply to an argument x, that is a status of a process,
+   as returned by waitpid().
+   On nearly all systems, including Linux/x86, WEXITSTATUS are bits 15..8 and
+   WTERMSIG are bits 7..0, while BeOS uses the opposite.  Therefore programs
+   have to use the abstract macros.  */
+
+/* For valid x, exactly one of WIFSIGNALED(x), WIFEXITED(x), WIFSTOPPED(x)
+   is true.  */
+# ifndef WIFSIGNALED
+#  define WIFSIGNALED(x) (WTERMSIG (x) != 0 && WTERMSIG(x) != 0x7f)
+# endif
+# ifndef WIFEXITED
+#  define WIFEXITED(x) (WTERMSIG (x) == 0)
+# endif
+# ifndef WIFSTOPPED
+#  define WIFSTOPPED(x) (WTERMSIG (x) == 0x7f)
+# endif
+
+/* The termination signal. Only to be accessed if WIFSIGNALED(x) is true.  */
+# ifndef WTERMSIG
+#  define WTERMSIG(x) ((x) & 0x7f)
+# endif
+
+/* The exit status. Only to be accessed if WIFEXITED(x) is true.  */
+# ifndef WEXITSTATUS
+#  define WEXITSTATUS(x) (((x) >> 8) & 0xff)
+# endif
+
+/* True if the process dumped core.  Not standardized by POSIX.  */
+# ifndef WCOREDUMP
+#  define WCOREDUMP(x) ((x) & 0x80)
+# endif
+
+# ifdef __cplusplus
+extern "C" {
+# endif
+
+/* Declarations of functions.  */
+
+# ifdef __cplusplus
+}
+# endif
+
+#else
+/* Native Windows API.  */
+
+# include <process.h>
+
+# define waitpid(pid,statusp,options) _cwait (statusp, pid, WAIT_CHILD)
+
+/* The following macros apply to an argument x, that is a status of a process,
+   as returned by waitpid() or, equivalently, _cwait() or GetExitCodeProcess().
+   This value is simply an 'int', not composed of bit fields.  */
+
+/* When an unhandled fatal signal terminates a process, the exit code is 3.  */
+# define WIFSIGNALED(x) ((x) == 3)
+# define WIFEXITED(x) ((x) != 3)
+# define WIFSTOPPED(x) 0
+
+/* The signal that terminated a process is not known posthum.  */
+# define WTERMSIG(x) SIGTERM
+
+# define WEXITSTATUS(x) (x)
+
+/* There are no core dumps.  */
+# define WCOREDUMP(x) 0
+
+#endif
+
+#endif /* _GL_SYS_WAIT_H */
+#endif /* _GL_SYS_WAIT_H */