swift234

Miscellaneous fixes to cope with typed collections in Foundation.

Swift's Dictionary and Set require their key and element type,
respectively, to be a Hashable type. When importing and bridging an
unspecialized NSDictionary or NSSet, we use 'NSObject' to ensure that
we have type that we know conforms to Hashable. Extend that logic to
specialized NSDictionary and NSSet imports, so that, e.g.,
NSDictionary<id<NSCopying>, V> gets imported as Dictionary<NSObject,
V> rather than the semantically-invalid Dictionary<NSCopying, V>.

Also, when importing a type that refers to an Objective-C type
parameter, don't introduce a typedef for the type parameter: just look
through it to the bound for now.

Swift SVN r24900