swift234

[arc-opts] Clear the state of the optimizer when we see autorelease push/pops.

I originally was not going to put this in for WWDC since we don't expect
people to really be using autorelease push/pops. But I keep having
nightmares about this coming up and would rather not wait to find out
that it was needed later.

<rdar://problem/16744768>

Swift SVN r18024