swift234

Reimplement circularly check for protocol inheritance.

First, make it actually check for cycles properly. Second, pull it
into the checking of the protocol itself, rather than keeping it as a
separate pass that happens too late to be useful. Finally, put the
unchecked/checking/checked bits into the AST to avoid having to keep a
separate DenseMap just for this purpose. Fixes <rdar://problem/14750346>.


Swift SVN r7324