fix for KT-237. Unit as value part

stdlib/src/jet/Tuple0.java

@@ -0,0 +1,26 @@
+package jet;
+
+/**
+ * @author alex.tkachman
+ */
+public class Tuple0 {
+    public static final Tuple0 INSTANCE = new Tuple0();
+
+    private Tuple0() {
+    }
+
+    @Override
+    public String toString() {
+        return "()";
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        return o == INSTANCE;
+    }
+
+    @Override
+    public int hashCode() {
+        return 239;
+    }
+}