Adds helper to create Shrink using LazyList

This allows to use Shrink from scala 2.13 without getting deprecation
warnings on scala.collection.immutable.Stream

src/main/scala-2.13+/org/scalacheck/LazyListShrink.scala

@@ -0,0 +1,17 @@
+/*-------------------------------------------------------------------------*\
+**  ScalaCheck                                                             **
+**  Copyright (c) 2007-2019 Rickard Nilsson. All rights reserved.          **
+**  http://www.scalacheck.org                                              **
+**                                                                         **
+**  This software is released under the terms of the Revised BSD License.  **
+**  There is NO WARRANTY. See the file LICENSE for the full text.          **
+\*------------------------------------------------------------------------ */
+package org.scalacheck
+
+/**
+ * Compatibility helper to create Shrinks using LazyList
+ */
+object LazyListShrink {
+  /** Forward to Shrink instance factory */
+  def apply[T](s: T => LazyList[T]): Shrink[T] = Shrink(s.andThen(_.toStream))
+}