swift234

[sil-arc] Casts do not use pointers in an interesting way.

The reason that this is true is that if the cast is dead, we will delete
it. If it is not dead there must be some other use after the cast that
uses our pointer via the cast. If that is true and there is a release
after that use we will not move the release over the use. On the other
hand if the release is in between the cast and the use it is of course
safe to move the release forward.

Swift SVN r16797