Two fixes here:
1) Actually check if the ApplyExpr's base is self, instead of assuming
that anything other than a super call is a constructor call on self, to
avoid flagging UnresolvedConstructorExprs formed from Metatype.init()
calls as delegations.
2) Sometimes this is called after parts of the body has been type checked,
here we had the opposite problem, a ConstructorRefCallExpr of a
constructor on self wasn't detected as such.
Fixes <rdar://problem/21914985>.
Swift SVN r30852
