Merge GDB 7.5.1

gdb/gnulib/import/m4/stddef_h.m4

 dnl A placeholder for POSIX 2008 <stddef.h>, for platforms that have issues.
-# stddef_h.m4 serial 2
-dnl Copyright (C) 2009, 2010, 2011 Free Software Foundation, Inc.
+# stddef_h.m4 serial 4
+dnl Copyright (C) 2009-2012 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_STDDEF_H],
 [
   AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
   AC_REQUIRE([gt_TYPE_WCHAR_T])
+  STDDEF_H=
   if test $gt_cv_c_wchar_t = no; then
     HAVE_WCHAR_T=0
     STDDEF_H=stddef.h
   fi
   AC_CACHE_CHECK([whether NULL can be used in arbitrary expressions],
     [gl_cv_decl_null_works],
     [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stddef.h>
       int test[2 * (sizeof NULL == sizeof (void *)) -1];
 ]])],
       [gl_cv_decl_null_works=yes],
       [gl_cv_decl_null_works=no])])
   if test $gl_cv_decl_null_works = no; then
     REPLACE_NULL=1
     STDDEF_H=stddef.h
   fi
+  AC_SUBST([STDDEF_H])
+  AM_CONDITIONAL([GL_GENERATE_STDDEF_H], [test -n "$STDDEF_H"])
   if test -n "$STDDEF_H"; then
-    gl_CHECK_NEXT_HEADERS([stddef.h])
+    gl_NEXT_HEADERS([stddef.h])
   fi
 ])
 
 AC_DEFUN([gl_STDDEF_MODULE_INDICATOR],
 [
   dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
   AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
 ])
 
 AC_DEFUN([gl_STDDEF_H_DEFAULTS],
 [
   dnl Assume proper GNU behavior unless another module says otherwise.
   REPLACE_NULL=0;                AC_SUBST([REPLACE_NULL])
   HAVE_WCHAR_T=1;                AC_SUBST([HAVE_WCHAR_T])
-  STDDEF_H='';                   AC_SUBST([STDDEF_H])
 ])