* Added a comment to vm_remove_all_page_mappings() that shows that we need to
change the mapping spinlock into a mutex.
* Pointed out some potential problems in the code.
* Added vm_page_at_index(), vm_clear_map_activation(), and vm_test_map_activation()
in preparation of the page scanner rewrite.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@20407 a95241bf-73f2-0310-859d-f6bbb57e9c96