swift234

fix a bug in code synthesized by the clang importer.  The "/*Implicit=*/true"
marker isn't actually setting the implicit bit, it was setting the "trailing 
closure" bit, for something that isn't of function type.  The effect of this
was to cause sema to eat the rawValue: parameter without requiring the label.

Instead of generating this code that happened to work out most of the time,
build the proper TupleExpr with the right parameter label.  NFC.



Swift SVN r31597