swift

31c1dc7e - Add support for specifying target in @lifetime

Add support for specifying target in @lifetime @lifetime(target: source1, source2...) where target can be any parameter or 'self'. We cannot have @lifetime attributes with duplicate targets. Also, update the internal data structures. Previously LifetimeEntry stored pairwise (target, source) dependencies. Now, LifetimeEntry will store an optional target descriptor and an array of source descriptors.