swift234

Fix bottom-up processing of tuple exprs in two ways:
1. Single-element tuples with names are not grouping parens.
2. Redo Sema of a tuple if we do propagate a type into it.

Also, remove the previous hack for trying to make:
  var e : ZeroOneTwoThree = :Three(1, 2, 3)

Unambiguous.  While it would be nice, it isn't essential and it clutters the model.


Swift SVN r308