- added a memory limitation in the zip parser and the pdf parser
- added a search throttling: if there are too many search queries are still to be computed, then new requests are not accepted for some time. if after a one second still no space is there to perform another search, the search terminates with no results. this case should only happen in case of DoS-like situations and in case of strong load on a peer like if it is integrated in metager.
- added a search cache deletion process that removes search requests in case that throttling happens
git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@7766 6c8d7289-2bf4-0310-a012-ef5d649a1542
