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/langinfo_h.m4

@@ -0,0 +1,105 @@
+# langinfo_h.m4 serial 7
+dnl Copyright (C) 2009-2010 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.
+
+AC_DEFUN([gl_LANGINFO_H],
+[
+  AC_REQUIRE([gl_LANGINFO_H_DEFAULTS])
+
+  dnl Persuade glibc-2.0.6 <langinfo.h> to define CODESET.
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+  dnl <langinfo.h> is always overridden, because of GNULIB_POSIXCHECK.
+  gl_CHECK_NEXT_HEADERS([langinfo.h])
+
+  dnl Determine whether <langinfo.h> exists. It is missing on mingw and BeOS.
+  HAVE_LANGINFO_CODESET=0
+  HAVE_LANGINFO_T_FMT_AMPM=0
+  HAVE_LANGINFO_ERA=0
+  HAVE_LANGINFO_YESEXPR=0
+  AC_CHECK_HEADERS_ONCE([langinfo.h])
+  if test $ac_cv_header_langinfo_h = yes; then
+    HAVE_LANGINFO_H=1
+    dnl Determine what <langinfo.h> defines. CODESET and ERA etc. are missing
+    dnl on OpenBSD 3.8. T_FMT_AMPM and YESEXPR, NOEXPR are missing on IRIX 5.3.
+    AC_CACHE_CHECK([whether langinfo.h defines CODESET],
+      [gl_cv_header_langinfo_codeset],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM([[#include <langinfo.h>
+int a = CODESET;
+]])],
+         [gl_cv_header_langinfo_codeset=yes],
+         [gl_cv_header_langinfo_codeset=no])
+      ])
+    if test $gl_cv_header_langinfo_codeset = yes; then
+      HAVE_LANGINFO_CODESET=1
+    fi
+    AC_CACHE_CHECK([whether langinfo.h defines T_FMT_AMPM],
+      [gl_cv_header_langinfo_t_fmt_ampm],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM([[#include <langinfo.h>
+int a = T_FMT_AMPM;
+]])],
+         [gl_cv_header_langinfo_t_fmt_ampm=yes],
+         [gl_cv_header_langinfo_t_fmt_ampm=no])
+      ])
+    if test $gl_cv_header_langinfo_t_fmt_ampm = yes; then
+      HAVE_LANGINFO_T_FMT_AMPM=1
+    fi
+    AC_CACHE_CHECK([whether langinfo.h defines ERA],
+      [gl_cv_header_langinfo_era],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM([[#include <langinfo.h>
+int a = ERA;
+]])],
+         [gl_cv_header_langinfo_era=yes],
+         [gl_cv_header_langinfo_era=no])
+      ])
+    if test $gl_cv_header_langinfo_era = yes; then
+      HAVE_LANGINFO_ERA=1
+    fi
+    AC_CACHE_CHECK([whether langinfo.h defines YESEXPR],
+      [gl_cv_header_langinfo_yesexpr],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM([[#include <langinfo.h>
+int a = YESEXPR;
+]])],
+         [gl_cv_header_langinfo_yesexpr=yes],
+         [gl_cv_header_langinfo_yesexpr=no])
+      ])
+    if test $gl_cv_header_langinfo_yesexpr = yes; then
+      HAVE_LANGINFO_YESEXPR=1
+    fi
+  else
+    HAVE_LANGINFO_H=0
+  fi
+  AC_SUBST([HAVE_LANGINFO_H])
+  AC_SUBST([HAVE_LANGINFO_CODESET])
+  AC_SUBST([HAVE_LANGINFO_T_FMT_AMPM])
+  AC_SUBST([HAVE_LANGINFO_ERA])
+  AC_SUBST([HAVE_LANGINFO_YESEXPR])
+
+  dnl Check for declarations of anything we want to poison if the
+  dnl corresponding gnulib module is not in use.
+  gl_WARN_ON_USE_PREPARE([[#include <langinfo.h>
+    ]], [nl_langinfo])
+])
+
+AC_DEFUN([gl_LANGINFO_MODULE_INDICATOR],
+[
+  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
+  AC_REQUIRE([gl_LANGINFO_H_DEFAULTS])
+  gl_MODULE_INDICATOR_SET_VARIABLE([$1])
+  dnl Define it also as a C macro, for the benefit of the unit tests.
+  gl_MODULE_INDICATOR_FOR_TESTS([$1])
+])
+
+AC_DEFUN([gl_LANGINFO_H_DEFAULTS],
+[
+  GNULIB_NL_LANGINFO=0;  AC_SUBST([GNULIB_NL_LANGINFO])
+  dnl Assume proper GNU behavior unless another module says otherwise.
+  HAVE_NL_LANGINFO=1;    AC_SUBST([HAVE_NL_LANGINFO])
+  REPLACE_NL_LANGINFO=0; AC_SUBST([REPLACE_NL_LANGINFO])
+])