swift234

Refactor ArchetypeBuilder to work with abstract generic parameters.

Have ArchetypeBuilder key the archetypes it produces by the abstract {depth,index} position of generic parameters rather than by the identity of particular GenericTypeParamDecls. Tighten the signature of AbstractTypeParamDecl-taking methods to only take GenericTypeParamDecls; that's the only case that comes up anymore. Introduce 'addGenericParameter' and 'getArchetype' overloads that work with GenericTypeParamTypes and DependentMemberTypes in addition to those that work with GenericTypeParamDecls.
Move ArchetypeBuilder.cpp from 'Sema' to 'AST' to correspond to its header's location.

When we parse something like 'protocol P { protocol Q {} }', eagerly give the erroneous nested protocol Q an ErrorType to suppress type-checking of the declaration. Otherwise, the nested implicit 'Self' parameters, which are fixed depth 0 index 0 in the generic parameter space, will collide in the ArchetypeBuilder.

Swift SVN r10966