swift234

Re-factoring: Make castTupleReturnType a utility function. NFC.

Moves castTupleReturnType from Devirtualize.cpp into Local.cpp, so that it can be re-used by other passes, e.g. simplify-cfg.
The ordering of castTupleReturnType's parameters and their types are cosmetically improved. But no functionality is changed.

Swift SVN r32555