(Bug 61715) Make history entries look at most recent revision

The problem with history thingies is that "restore" should not show up for users
that can not view the permissions for what is restored.
isAllowed will check the most recent revision to get some sort of "global
allowed state" for a revision. Combined with the above, this would make any
revision of a just-restored post be invisible.
For that reason, I had made history (and RC) permission checks only do
isRevisionAllowed. That's incorrect; they should also check last revision (but
in a way that is actually correct - where the restore-aspect is ignored for the
"global" moderation state)

Bug: 61715
Change-Id: Ia27c94176bb8f40f2fe683a54ab9ddafb4f98fc0
Merge "(Bug 61715) Make history entries look at most recent revision"