SIL: Private methods of open resilient classes don't need to be public

Private methods of non-resilient classes can be referenced from
outside the module, but resilient classes build the vtable at
runtime so we don't need that hack there.

lib/SIL/SILDeclRef.cpp

@@ -912,6 +912,8 @@ SubclassScope SILDeclRef::getSubclassScope() const {
   case AccessLevel::Public:
     return SubclassScope::Internal;
   case AccessLevel::Open:
+    if (classType->isResilient())
+      return SubclassScope::Internal;
     return SubclassScope::External;
   }