swift234

HACK: implement === for NSObject using a runtime function.

Clearly not ideal, but
(1) there's no conversion from id to RawPointer without using the
    Builtin module
(2) there's no way to import the Builtin module and the standard library
    (which is a good thing)
(3) Swift modules are currently translation units, so we can't have a
    separate Identity.swift that gets compiled into libswiftFoundation
    <rdar://problem/13075215>

Swift SVN r3853