Add synthetic argument to default constructors

It's need to add synthetic argument (of type that user can't use)
to constructors with default arguments to avoid clashing with
real user's constructor having the same set of parameters
and additional int's arguments.

core/runtime.jvm/src/kotlin/jvm/internal/DefaultConstructorMarker.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2010-2015 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package kotlin.jvm.internal;
+
+final class DefaultConstructorMarker {
+    private DefaultConstructorMarker() {}
+}