Fix Use-after-free segfault in ap_server_config_defines seen on start-up on OpenBSD

Reported by Sam Vaughan at https://bz.apache.org/bugzilla/show_bug.cgi?id=63516
Suggested fix by Joe Orton on that ticket.

git-svn-id: https://svn.apache.org/repos/asf/perl/modperl/trunk@1861755 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/modules/perl/mod_perl.c b/src/modules/perl/mod_perl.c
index 1e17747..23dcda6 100644
--- a/src/modules/perl/mod_perl.c
+++ b/src/modules/perl/mod_perl.c
@@ -861,7 +861,7 @@
 
     /* for <IfDefine MODPERL2> and Apache2->define("MODPERL2") */
     *(char **)apr_array_push(ap_server_config_defines) =
-        apr_pstrdup(p, "MODPERL2");
+        apr_pstrdup(ap_server_config_defines->pool, "MODPERL2");
 
     ap_hook_pre_config(modperl_hook_pre_config,
                        NULL, NULL, APR_HOOK_MIDDLE);