Treat SEALED_SUBCLASS_FQ_NAME_LIST change as a class signature change

#KT-19580

jps-plugin/testData/incremental/classHierarchyAffected/sealedClassNestedImplAdded/use.kt

@@ -0,0 +1,7 @@
+import Base.*
+
+fun use(x: Base): String =
+        when (x) {
+            is A -> "A"
+            is B -> "B"
+        }