swift234

Fix -[NSUndoManager prepareWithInvocationTarget:].

This method returns a proxy object. Swift cannot current cast proxy objects 
to their proxied types. The workaround for now is to add a generic overlay 
for -prepareWithInvocationTarget: so the declared type of the returned 
proxy is the proxied type. This is good enough to make undo proxies work with 
objc-dispatched calls.


Swift SVN r18155