The original code had at least two OpenACS caused memory leaks: it led
to an unbounded growth for __template_cache_value and did not unset
the nsv variables __template_*_timeout. This bug led openacs.org to a
broken state (forums posting lead to the message "Not enough memory to
allocate the list internal rep"). The new code makes use of the per
entry expire feature of ns_cache and emulates the behavior otherwise.
