Destroy ACLs in the reverse order of creation to avoid destruction segfaults
during reconfiguration.

Group ACLs created later may use other ACLs created earlier. A group ACL must
be deleted first so that its AclDeleter can safely access registration status
(and avoid double deletion) of the ACLs it uses. Since ACLs are remembered (in
Config.aclList) using a singly-linked list, it is difficult to change their
deletion order.  Instead, we change their listing order from FIFO to LIFO.

=== modified file 'src/acl/Acl.cc'
--- src/acl/Acl.cc	2013-08-29 09:21:53 +0000
+++ src/acl/Acl.cc	2013-11-28 23:56:07 +0000
@@ -278,47 +278,45 @@ ACL::ParseAclLine(ConfigParser &parser, 
     /*split the function here */
     A->parse();
 
     /*
      * Clear AclMatchedName from our temporary hack
      */
     AclMatchedName = NULL;	/* ugly */
 
     if (!new_acl)
         return;
 
     if (A->empty()) {
         debugs(28, DBG_CRITICAL, "Warning: empty ACL: " << A->cfgline);
     }
 
     if (!A->valid()) {
         fatalf("ERROR: Invalid ACL: %s\n",
                A->cfgline);
     }
 
-    /* append */
+    // prepend so that ACLs declared later (and possibly using earlier ACLs)
+    // are destroyed earlier (before the ACLs they use are destroyed)
     assert(head && *head == Config.aclList);
     A->registered = true;
-
-    while (*head)
-        head = &(*head)->next;
-
+    A->next = *head;
     *head = A;
 }
 
 bool
 ACL::isProxyAuth() const
 {
     return false;
 }
 
 /* ACL result caching routines */
 
 int
 ACL::matchForCache(ACLChecklist *checklist)
 {
     /* This is a fatal to ensure that cacheMatchAcl calls are _only_
      * made for supported acl types */
     fatal("aclCacheMatchAcl: unknown or unexpected ACL type");
     return 0;		/* NOTREACHED */
 }