swift234

Rewrite most of DI to work on the entire memory object at once,
instead of working a tuple-element at a time.  This requires it
to use bitvectors to compute each tuple element's liveness separately.

A big part of this is introducing the new MemoryUse type, which wraps
up the tuple elements accessed by a user of the memory object in addition
to its kind, and extending the NonLoadUses set to keep an index into the
Uses map, and a lot of other things.

This wraps up:
<rdar://problem/15228619> Eliminate the notion of Element from DefiniteInitialization



Swift SVN r10520