Add new input needed for test/Constraints/dynamic_lookup.swift.

Author: DougGregor

test/Constraints/Inputs/PrivateObjC.swift

@@ -0,0 +1,9 @@
+import Foundation
+
+public class PrivateObjC {
+  @objc private func privateFoo() { }
+}
+
+public class InternalObjC {
+  @objc internal func internalFoo() { }
+}