swift234

[ClangImporter] Resolve @partial_interface to a Swift class, like @class.

@partial_interface is like @class, but it allows the user to write categories
or (eventually) subclasses in their Objective-C headers even though the
class will be implemented in Swift. The resolution rules are thus exactly the
same as for class.

I've included a template hack to allow you to keep building without switching
to the new internal Clang repo; in this case you will see one test failure.

<rdar://problem/16426884>

Swift SVN r15523