Before the patch, HTMLPurifier was instructed to handle <nolink>
tags in block mode. That implies that any block tag enclosing it
had to be closed for HTML compliance.
But <noscript> tags are not part of the final output (they are
removed) but just internally used to skip filtering certain areas.
So they can be virtually everywhere, HTMLPurifier just should allow
them without any change, both to parent or children tags.
The improvements include:
* HTMLPurifier cache is stored in localcachedir
* allowobjectembed changes are not ignored any more
* the cache keys include revision and all options which makes
this suitable for local caches on cluster nodes
* unchanged test is replaced by "true" value which should
significantly improve performance
* removal of purge_all_caches() hack for directory recreation
* comments and coding style cleanup
