swift234

Import DarwinBoolean as Bool in fully-bridgeable contexts.

These are contexts where we have enough information to bridge /back/
properly; that is, where we can distinguish CBool, ObjCBool, and
DarwinBoolean. In cases where we can't, we keep the three separate;
only CBool is really the same type as Bool.

This also affects current import behavior for ObjCBool, which was previously
incorrectly conflated with CBool in certain cases.

More rdar://problem/19013551

Swift SVN r30051