Objective C Bridge

There is the start of an Objective C bridge available.

Notably, it lacks support for objc_msgSend.

We need a design for how this should work, preferably informed by other implementations. Some Common Lisp implementations have Objective C bridges and may be a good place to look.

In Dylan, this may require some compiler support, similar to direct-c-ffi or the higher level c-ffi.

BridgeSupport

We should be able to have melange read in BridgeSupport files and generate the appropriate bindings as defined in interface files like we do for C APIs.

Subclassing and New Methods

The Objective C 2.0 runtime provides enough support to allow Dylan programs to create new subclasses of Objective C classes as well as to expose new method implementations.

Optimizing to use objc_msgSend_vtable

We will need compiler support to do this correctly, but some invocations of objc_msgSend could, in fact, become invocations of the objc_msgSend_vtable* functions. The code generated should actually be using objc_msgSend_fixup in this situation to enable this optimization within the Objective C run-time.

For details, see `[objc explain]: objc_msgSend_vtable`_ by Greg Parker.