Workaround for scaladoc failure.

Addressing this little fellow:

21:40:22   [scaladoc] src/library/scala/collection/TraversableOnce.scala:382: error: missing parameter type for expanded function
21:40:22   [scaladoc] The argument types of an anonymous function must be fully known. (SLS 8.5)
21:40:22   [scaladoc] Expected type was: _[?] => Coll[A]
21:40:22   [scaladoc]       case xs: generic.GenericTraversableTemplate[_, _] => xs.genericBuilder mapResult {
21:40:22   [scaladoc]                                                                                        ^

src/library/scala/collection/TraversableOnce.scala

@@ -379,7 +379,7 @@ object TraversableOnce {
      *  @return the result of invoking the `genericBuilder` method on `from`.
      */
     def apply(from: Coll[_]): Builder[A, Coll[A]] = from match {
-      case xs: generic.GenericTraversableTemplate[_, _] => xs.genericBuilder mapResult {
+      case xs: generic.GenericTraversableTemplate[_, _] => xs.genericBuilder.asInstanceOf[Builder[A, Traversable[A]]] mapResult {
         case res => traversableToColl(res.asInstanceOf[GenTraversable[A]])
       }
       case _ => newIterator