Add test case for bug that's already fixed

Author: slavapestov

validation-test/compiler_crashers_2_fixed/0166-rdar30168645.swift

@@ -0,0 +1,7 @@
+// RUN: %target-swift-frontend %s -emit-ir
+
+protocol P {}
+
+class Base<T: P> {}
+
+class Derived: Base<Derived>, P {}