{Prepare,Commit,Cancel}Modifications() using the userland add-on
backend. IsModified() and CommitModifications() are little more than
stubs ATM.
* Made BPartition::VisitEachChild()/VisitEachDescendant() const.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22602 a95241bf-73f2-0310-859d-f6bbb57e9c96