swift234

SILGen: Recursively destructure tuple arguments.
Fully and consistently destructure tuples when in a function argument context, and require that ApplyInst always take destructured arguments corresponding to the lowered argument types as its inputs. This eliminates a ton of finicky special-case code all over the place and also has the nice fringe benefit of avoiding a bunch of useless TupleInsts that were being emitted before. Currently this breaks variadic tuple fields and argument writeback. I'll fix variadic tuple fields soon. The argument writeback sucked anyway and I'll do it right later.

Swift SVN r3730