swift234

Rework a bunch of stuff in the type system: now the *only* way to name a type is through a 'typealias' and there is no such thing as a OneOfDecl.  Instead, we have OneOfType's, which are always anonymous.  "oneof declarations" and "struct declarations" are now both just sugar.

This eliminates the NamedTypeDecl class (because there is now only one named type decl), eliminates OneOfDecl, renames AliasTypeDecl to NameAliasTypeDecl for good measure, and introduces OneOfType.

This preserves all existing syntax, and allows stuff like this:

func test6(checkboxenabled : oneof { Yep, Nope }) {
  test6(:Yep)
}

Which is an anonymous oneof.

Swift SVN r237