Make Ref classes for shared vars Serializable

#KT-14566 Fixed

compiler/testData/codegen/box/closures/refsAreSerializable.kt

@@ -0,0 +1,34 @@
+// IGNORE_BACKEND: JS
+
+import java.io.*
+
+fun box(): String {
+    var o = ""
+    var b = 0.toByte()
+    var d = 0.0
+    var f = 0.0f
+    var i = 0
+    var j = 0L
+    var s = 0.toShort()
+    var c = '0'
+    var z = false
+
+    val lambda = fun(): String {
+        o = "OK"
+        b++; d++; f++; i++; j++; s++; c++
+        z = true
+        return o
+    }
+
+    val baos = ByteArrayOutputStream()
+    val oos = ObjectOutputStream(baos)
+    oos.writeObject(lambda)
+    oos.close()
+
+    val bais = ByteArrayInputStream(baos.toByteArray())
+    val ois = ObjectInputStream(bais)
+    val result = ois.readObject() as () -> String
+    ois.close()
+
+    return result()
+}