- Use virtual dispatch to localize some predicates instead
of having special cases for LetValue inits in global places.
- Improve 'const'ness of methods.
- Introduce a common "KnownAddressInitialization" class to centralize
the notion of an initialization corresponding to a specific physical
address that is known up front. Consolidate dupes of this concept into
uses of it.
NFC.
Swift SVN r27462