mktime, mktime-internal: Remove obsolete code

[Bruno Haible]

This patch removes a workaround against a problem that was fixed on 2007-11-01.


2020-08-14  Bruno Haible  <bruno@clisp.org>

        mktime, mktime-internal: Remove obsolete code.
        * m4/mktime.m4 (gl_FUNC_MKTIME_WORKS): Don't #undef putenv.

diff --git a/m4/mktime.m4 b/m4/mktime.m4
index afc8a87..917e759 100644
--- a/m4/mktime.m4
+++ b/m4/mktime.m4
@@ -1,4 +1,4 @@
-# serial 33
+# serial 34
 dnl Copyright (C) 2002-2003, 2005-2007, 2009-2020 Free Software Foundation,
 dnl Inc.
 dnl This file is free software; the Free Software Foundation
@@ -58,9 +58,6 @@ AC_DEFUN([gl_FUNC_MKTIME_WORKS],
 # define TIME_T_IS_SIGNED 0
 #endif
 
-/* Work around redefinition to rpl_putenv by other config tests.  */
-#undef putenv
-
 static time_t time_t_max;
 static time_t time_t_min;