allocate with the vm_cache locked - this is necessary to be able to steal pages
from itself (large files...).
The system doesn't actually lock up anymore, but it still renders itself unusable;
obviously the page thief does not work correctly, yet. The rest of the experience
is created by our current scheduler (the page thief runs and runs, but it doesn't
free any pages anymore).
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22466 a95241bf-73f2-0310-859d-f6bbb57e9c96
20b232e900