swift234

Progress towards implementing SE-0049 - Allow autoclosure in parameter types
as well as on parameter decls.  Also, tighten up the type checker to look at
parameter types instead of decl attributes in some cases (exposing a type
checker bug).

Still TODO:
 - Reject autoclosure/noescape on non-parameter types.
 - Move stdlib and other code to use noescape and autoclosure in the right
   spot.
 - Warn about autoclosure/noescape on parameters decls, with a fixit to move it.
 - Upgrade the warning to an error.