swift234

SILGen: When emitting a partial application thunk for a dynamic method, convert @autoreleased result to @owned

In IRGen, @autoreleased return values are always converted to +1 by
calling objc_retainAutoreleasedReturnValue(), so a partial application
thunk cannot have a result with @autoreleased convention. Just turn
it into @owned instead, since that's what it is, using similar logic
as the @unowned_inner_pointer => @unowned case.

Fixes <rdar://problem/24805609>.