Add a parameter list to EnumElementDecl

This models, but does not plumb through, default arguments.

include/swift/Serialization/ModuleFormat.h

@@ -55,7 +55,8 @@ const uint16_t VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t VERSION_MINOR = 404; // Last change: inheritsSuperclassInitializers
+
+const uint16_t VERSION_MINOR = 405; // Last change: EnumElementDecl has a ParameterList
 
 using DeclIDField = BCFixed<31>;
 
@@ -1083,14 +1084,18 @@ namespace decls_block {
 
   using EnumElementLayout = BCRecordLayout<
     ENUM_ELEMENT_DECL,
-    IdentifierIDField, // name
     DeclContextIDField,// context decl
     TypeIDField, // interface type
-    BCFixed<1>,  // has argument type?
     BCFixed<1>,  // implicit?
+    BCFixed<1>,  // has payload?
     EnumElementRawValueKindField,  // raw value kind
     BCFixed<1>,  // negative raw value?
-    BCBlob       // raw value
+    IdentifierIDField, // raw value
+    BCVBR<5>, // number of parameter name components
+    BCArray<IdentifierIDField> // name components,
+
+    // The record is trailed by:
+    // - its argument parameters, if any
   >;
 
   using SubscriptLayout = BCRecordLayout<