supporting autoconf < 2.60

[Bruno Haible]

This fixes an error when autoconf 2.59 and automake 1.9.6 are used.

$ ./gnulib-tool --test quotearg
...
executing autoconf
configure:4339: error: possibly undefined macro: AC_COMPUTE_INT
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.


2008-12-17  Bruno Haible  <address@hidden>

        * m4/errno_h.m4 (AC_COMPUTE_INT): Provide fallback definition.

--- m4/errno_h.m4.orig  2008-12-18 03:20:42.000000000 +0100
+++ m4/errno_h.m4       2008-12-18 03:18:53.000000000 +0100
@@ -1,4 +1,4 @@
-# errno_h.m4 serial 1
+# errno_h.m4 serial 2
 dnl Copyright (C) 2004, 2006, 2008 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -111,3 +111,9 @@
     AC_SUBST($1[_VALUE])
   fi
 ])
+
+dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in.
+dnl Remove this when we can assume autoconf >= 2.61.
+m4_ifdef([AC_COMPUTE_INT], [], [
+  AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])])
+])