Accept ObjC API wrapper types as arguments and return values from
bound Go package functions and methods. Also, allow Go structs
to extend ObjC classes and implement ObjC protocols as well as override
and implement methods.
This is the third and final part of the implementation of the golang/go#17102
proposal.
Fixesgolang/go#17102
Change-Id: I601d90fb6d22b8d6f8b7d5fe0130daa1a4dd4734
Reviewed-on: https://go-review.googlesource.com/29175
Reviewed-by: David Crawshaw <crawshaw@golang.org>
