Update to gettext 0.18.3.1, fix AC_CHECK_DECLS usage

m4/intl.m4

-# intl.m4 serial 23 (gettext-0.18.3)
+# intl.m4 serial 24 (gettext-0.18.3)
 dnl Copyright (C) 1995-2013 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -61,7 +61,7 @@ AC_DEFUN([AM_INTL_SUBDIR],
 
   dnl Use the _snprintf function only if it is declared (because on NetBSD it
   dnl is defined as a weak alias of snprintf; we prefer to use the latter).
-  AC_CHECK_DECLS([_snprintf _snwprintf], , , [#include <stdio.h>])
+  AC_CHECK_DECLS([_snprintf, _snwprintf], , , [#include <stdio.h>])
 
   dnl Use the *_unlocked functions only if they are declared.
   dnl (because some of them were defined without being declared in Solaris
@@ -234,7 +234,7 @@ AC_DEFUN([gt_INTL_SUBDIR_CORE],
   dnl (because some of them were defined without being declared in Solaris
   dnl 2.5.1 but were removed in Solaris 2.6, whereas we want binaries built
   dnl on Solaris 2.5.1 to run on Solaris 2.6).
-  AC_CHECK_DECLS([feof_unlocked fgets_unlocked], , , [#include <stdio.h>])
+  AC_CHECK_DECLS([feof_unlocked, fgets_unlocked], , , [#include <stdio.h>])
 
   AM_ICONV