Some cases of using isSuperset can cause crashes, this was caused by improper subclassing callouts; this pr resolves those failures (and provides unit tests for that case)
The cases where the bridge was traversed too much now only causes a single bridge out call (without needing to reallocate or thrash retain/release)
String.components(separatedBy: CharacterSet) should be considerably faster now not only for more apporpriate bridging calls but also no longer needing to bridge arrays back and forth.
Resolves the following issues:
rdar://problem/17281998
rdar://problem/26611771
rdar://problem/29738989
