Introduce special name for destructors

This name is not used yet

include/swift/Serialization/ModuleFormat.h

@@ -54,7 +54,7 @@ const uint16_t VERSION_MAJOR = 0;
 /// in source control, you should also update the comment to briefly
 /// 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.
-const uint16_t VERSION_MINOR = 353; // Last change: count inherited conformances
+const uint16_t VERSION_MINOR = 354; // Last change: special destructor names
 
 using DeclID = PointerEmbeddedInt<unsigned, 31>;
 using DeclIDField = BCFixed<31>;
@@ -345,7 +345,8 @@ using OptionalTypeKindField = BCFixed<2>;
 // VERSION_MAJOR.
 enum class DeclNameKind: uint8_t {
   Normal,
-  Subscript
+  Subscript,
+  Destructor
 };
 
 // These IDs must \em not be renumbered or reordered without incrementing
@@ -359,6 +360,8 @@ enum SpecialIdentifierID : uint8_t {
   OBJC_HEADER_MODULE_ID,
   /// Special value for the special subscript name
   SUBSCRIPT_ID,
+  /// Special value for the special destructor name
+  DESTRUCTOR_ID,
 
   /// The number of special Identifier IDs. This value should never be encoded;
   /// it should only be used to count the number of names above. As such, it