Track the generic parameters and requirements of nominal type declarations.

Put generic nominal type declarations through the same dependent-type
validation as generic functions, then capture their generic parameters
and requirements in their generic signature. This allows us to
re-instate the requirements in their dependent forms, before the
archetypes ruin them completely.


Swift SVN r8958

lib/Serialization/ModuleFormat.h

@@ -320,6 +320,7 @@ namespace decls_block {
     GENERIC_PARAM_LIST = 240,
     GENERIC_PARAM,
     GENERIC_REQUIREMENT,
+    LAST_GENERIC_REQUIREMENT,
 
     NO_CONFORMANCE = 250,
     NORMAL_PROTOCOL_CONFORMANCE = 251,
@@ -762,6 +763,17 @@ namespace decls_block {
     BCArray<TypeIDField>         // types involved (currently always two)
   >;
 
+  /// Placeholder that marks the last generic requirement in the generic
+  /// parameters list.
+  ///
+  /// Used as a buffer between the generic parameter list's requirements and
+  /// the generic signature's requirements for nominal type declarations.
+  /// FIXME: Expected to go away once the latter is no longer serialized.
+  using LastGenericRequirementLayout = BCRecordLayout<
+    LAST_GENERIC_REQUIREMENT,
+    BCFixed<1>                 // dummy
+  >;
+
   /// A placeholder for lack of conformance information. Conformances are
   /// indexed, so simply omitting one would be incorrect.
   using NoConformanceLayout = BCRecordLayout<