necessary because low memory handlers might need to wait for other services
while we need to make sure the page thief can always steal pages.
* Made the page thief more aggressive when memory is critical: added a third
run where it will also steal a small amount of active pages to keep things
going.
* The page thief did not maintain the cache's reference correctly in all
situations.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22382 a95241bf-73f2-0310-859d-f6bbb57e9c96