swift234

AST: Include "Self" and associated archetypes in AllArchetypes of a GenericParamList.

The need to hide Self from AllArchetypes of a GenericParamList is (almost) defined away by @cc(witness_method); IRGen now knows how to do the right thing for witnesses regardless of their generic signature. Eliminating this special case from the AST allows us to clear up a bunch of ugly hacks that piled up elsewhere to try to accommodate that special case, and makes the prospect of moving IRGen's PolymorphicConvention to interface types more manageable.

We do need an unfortunate hack to suppress emitting associated archetypes of Self when considering an archetype as the polymorphic source for a witness, since we can't actually pass those through the witness CC without breaking ABI compatibility between generic signatures.

Swift SVN r13663