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/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/JvmAbi.java

@@ -25,7 +25,7 @@ public final class JvmAbi {
      * This constant is used to identify binary format (class file) versions
      * If you change class file metadata format and/or naming conventions, please increase this number
      */
-    public static final int VERSION = 20;
+    public static final int VERSION = 21;
 
     public static final String TRAIT_IMPL_CLASS_NAME = "$TImpl";
     public static final String TRAIT_IMPL_SUFFIX = "$" + TRAIT_IMPL_CLASS_NAME;