SI-5974 make collection.convert.Wrappers serializable

Author: lrytz

src/library/scala/collection/convert/Wrappers.scala

@@ -467,4 +467,5 @@ private[collection] trait Wrappers {
   }
 }
 
-object Wrappers extends Wrappers
+@SerialVersionUID(0 - 5857859809262781311L)
+object Wrappers extends Wrappers with Serializable

test/files/run/t5974.check

@@ -0,0 +1 @@
+ok

test/files/run/t5974.scala

@@ -0,0 +1,10 @@
+object Test extends App {
+  import scala.collection.JavaConverters._
+
+  def ser(a: AnyRef) =
+    (new java.io.ObjectOutputStream(new java.io.ByteArrayOutputStream())).writeObject(a)
+
+  val l = java.util.Arrays.asList("pigdog").asScala
+  ser(l)
+  println("ok")
+}