Added automake/autoconf system

gl/m4/stddef_h.m4

@@ -0,0 +1,47 @@
+dnl A placeholder for POSIX 2008 <stddef.h>, for platforms that have issues.
+# stddef_h.m4 serial 4
+dnl Copyright (C) 2009-2013 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_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])
+])