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.

m4/locale-zh.m4

@@ -0,0 +1,92 @@
+# locale-zh.m4 serial 6
+dnl Copyright (C) 2003, 2005-2010 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Bruno Haible.
+
+dnl Determine the name of a chinese locale with GB18030 encoding.
+AC_DEFUN([gt_LOCALE_ZH_CN],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_REQUIRE([AM_LANGINFO_CODESET])
+  AC_CACHE_CHECK([for a transitional chinese locale], [gt_cv_locale_zh_CN], [
+    AC_LANG_CONFTEST([AC_LANG_SOURCE([
+changequote(,)dnl
+#include <locale.h>
+#include <stdlib.h>
+#include <time.h>
+#if HAVE_LANGINFO_CODESET
+# include <langinfo.h>
+#endif
+#include <stdlib.h>
+#include <string.h>
+struct tm t;
+char buf[16];
+int main ()
+{
+  const char *p;
+  /* Check whether the given locale name is recognized by the system.  */
+  if (setlocale (LC_ALL, "") == NULL) return 1;
+  /* Check whether nl_langinfo(CODESET) is nonempty and not "ASCII" or "646".
+     On MacOS X 10.3.5 (Darwin 7.5) in the fr_FR locale, nl_langinfo(CODESET)
+     is empty, and the behaviour of Tcl 8.4 in this locale is not useful.
+     On OpenBSD 4.0, when an unsupported locale is specified, setlocale()
+     succeeds but then nl_langinfo(CODESET) is "646". In this situation,
+     some unit tests fail.  */
+#if HAVE_LANGINFO_CODESET
+  {
+    const char *cs = nl_langinfo (CODESET);
+    if (cs[0] == '\0' || strcmp (cs, "ASCII") == 0 || strcmp (cs, "646") == 0)
+      return 1;
+  }
+#endif
+#ifdef __CYGWIN__
+  /* On Cygwin, avoid locale names without encoding suffix, because the
+     locale_charset() function relies on the encoding suffix.  Note that
+     LC_ALL is set on the command line.  */
+  if (strchr (getenv ("LC_ALL"), '.') == NULL) return 1;
+#endif
+  /* Check whether in a month name, no byte in the range 0x80..0x9F occurs.
+     This excludes the UTF-8 encoding.  */
+  t.tm_year = 1975 - 1900; t.tm_mon = 2 - 1; t.tm_mday = 4;
+  if (strftime (buf, sizeof (buf), "%B", &t) < 2) return 1;
+  for (p = buf; *p != '\0'; p++)
+    if ((unsigned char) *p >= 0x80 && (unsigned char) *p < 0xa0)
+      return 1;
+  /* Check whether a typical GB18030 multibyte sequence is recognized as a
+     single wide character.  This excludes the GB2312 and GBK encodings.  */
+  if (mblen ("\203\062\332\066", 5) != 4)
+    return 1;
+  return 0;
+}
+changequote([,])dnl
+      ])])
+    if AC_TRY_EVAL([ac_link]) && test -s conftest$ac_exeext; then
+      # Setting LC_ALL is not enough. Need to set LC_TIME to empty, because
+      # otherwise on MacOS X 10.3.5 the LC_TIME=C from the beginning of the
+      # configure script would override the LC_ALL setting. Likewise for
+      # LC_CTYPE, which is also set at the beginning of the configure script.
+      # Test for the locale name without encoding suffix.
+      if (LC_ALL=zh_CN LC_TIME= LC_CTYPE= ./conftest; exit) 2>/dev/null; then
+        gt_cv_locale_zh_CN=zh_CN
+      else
+        # Test for the locale name with explicit encoding suffix.
+        if (LC_ALL=zh_CN.GB18030 LC_TIME= LC_CTYPE= ./conftest; exit) 2>/dev/null; then
+          gt_cv_locale_zh_CN=zh_CN.GB18030
+        else
+          # None found.
+          gt_cv_locale_zh_CN=none
+        fi
+      fi
+    else
+      # If there was a link error, due to mblen(), the system is so old that
+      # it certainly doesn't have a chinese locale.
+      gt_cv_locale_zh_CN=none
+    fi
+    rm -fr conftest*
+  ])
+  LOCALE_ZH_CN=$gt_cv_locale_zh_CN
+  AC_SUBST([LOCALE_ZH_CN])
+])