Automatically emit objc_msgSend calls when calling imported or implemented Objective-C methods

- Add intrinsics.objc_super()

- Emit objc_msgSendSuper2 calls when an objc method call is combined with objc_super(self)

- Fix objc_block return value ABI for large struct returns

- Fix objc_implement method wrappers bad ABI for large struct returns and indirect args

- Simplify parameter forwarding for objc_imlpement methods

- Add intrinsics.objc_instancetype to mimi Objective-C instancetype* returns
  This facilitates returning the correct type on subclasses when calling mehtods
  such as `alloc`, `init`, `retain`, etc.

- Refactor Objective-C class implementations generation so that hierarchies are properly initialized

- Better codegen for context passing with ivar-based autocontext

- Allow @superclass on imported objc-c objects

- Better codegen for block forwarding invoker, arguments are forwarded directly

src/parser.hpp

@@ -48,7 +48,8 @@ gb_global String const addressing_mode_strings[] = {
 struct TypeAndValue {
 	Type *         type;
 	AddressingMode mode;
-	bool           is_lhs; // Debug info
+	bool           is_lhs;            // Debug info
+	Type *         objc_super_target; // Original type of the Obj-C object before being converted to the superclass' type by the objc_super() intrinsic.
 	ExactValue     value;
 };