Category Permission Cache is calculated incorrectly on PHP5

Noticed that allow/deny category permissions are used for categories,
then they are incorrectly inherited (at least CATEGORY.VIEW permission). To
inherit permission kPermCacheUpdater class assigns permission object without
reference to copy it. This approach works in PHP4, because "=" is used
instead of "=&". PHP5 always passes objects by reference even if "=&"
operator is not used. This way we got random inheritance logic.

To solve this in PHP5 "clone" operator is used, but since this should work
in PHP4 too, then serialize/unserialize is used.