swift234

Completely remove the ability to do elementwise conversion of tuple values
to compatible-but-different tuple types, unless the tuple value is a tuple
literal (syntactically a paren expression).  This is both unnecessary except
in insane cases (see the testcase) and breaks some invariants that we'd like
to keep (like the AST being a tree).  Reordering of elements is still fine.


Swift SVN r383