Temporal AA sharpening

[hallatore]

@mittense

One more issue: when you squash your commits, it completely erases the history of any changes made in prior iterations (unless you stored them in another branch). Which means that, at least for folks like me that manage a fairly heavily-customized fork of UE, figuring out what changes to undo is kind of a pain, as it requires searching my own repo’s history to see the series of related commits. In this case, there was only the issue of a CVar being not taken care of, but: in general, squashing commits is not super helpful.

Not going to squash any more commits. It was mostly for the initial version.