prepare for autoconf-2.60

[Bruno Haible]

Hi,

It appears that autoconf-2.60 may be released soon. I added comments to
longdouble.m4 and onceonly.m4 relating to the new macros in autoconf-2.59d.
I also propose a similar comment to extensions.m4, see below.

Bruno

diff -c -3 -r1.5 longdouble.m4
*** longdouble.m4       18 Jan 2005 13:07:56 -0000      1.5
--- longdouble.m4       19 Apr 2006 11:35:28 -0000
***************
*** 1,5 ****
! # longdouble.m4 serial 1 (gettext-0.12)
! dnl Copyright (C) 2002-2003 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.
--- 1,5 ----
! # longdouble.m4 serial 2 (gettext-0.15)
! dnl Copyright (C) 2002-2003, 2006 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.
***************
*** 8,13 ****
--- 8,16 ----
  dnl Test whether the compiler supports the 'long double' type.
  dnl Prerequisite: AC_PROG_CC
  
+ dnl This file is only needed in autoconf <= 2.59.  Newer versions of autoconf
+ dnl have a macro AC_TYPE_LONG_DOUBLE with identical semantics.
+ 
  AC_DEFUN([gt_TYPE_LONGDOUBLE],
  [
    AC_CACHE_CHECK([for long double], gt_cv_c_long_double,
diff -c -3 -r1.6 onceonly.m4
*** onceonly.m4 3 Mar 2005 20:59:01 -0000       1.6
--- onceonly.m4 19 Apr 2006 11:35:28 -0000
***************
*** 1,5 ****
! # onceonly.m4 serial 3 (gettext-0.12)
! dnl Copyright (C) 2002, 2003 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.
--- 1,5 ----
! # onceonly.m4 serial 4 (gettext-0.15)
! dnl Copyright (C) 2002-2003, 2006 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.
***************
*** 19,24 ****
--- 19,29 ----
  dnl empty, and the check will be inserted before the body of the AC_DEFUNed
  dnl function.
  
+ dnl This file is only needed in autoconf <= 2.59.  Newer versions of autoconf
+ dnl have this macro built-in.  But about AC_CHECK_DECLS_ONCE: note that in
+ dnl autoconf >= 2.60 the symbol separator is a comma, whereas here it is
+ dnl whitespace.
+ 
  dnl Autoconf version 2.57 or newer is recommended.
  AC_PREREQ(2.54)
  
diff -c -3 -r1.9 extensions.m4
*** extensions.m4       2 Mar 2006 00:04:59 -0000       1.9
--- extensions.m4       19 Apr 2006 11:35:28 -0000
***************
*** 5,10 ****
--- 5,13 ----
  # gives unlimited permission to copy and/or distribute it,
  # with or without modifications, as long as this notice is preserved.
  
+ # This file is only needed in autoconf <= 2.59.  Newer versions of autoconf
+ # have a macro AC_USE_SYSTEM_EXTENSIONS with identical semantics.
+ 
  # gl_USE_SYSTEM_EXTENSIONS
  # ------------------------
  # Enable extensions on systems that normally disable them,