Increment scalacheck to 1.13.4 to fix 2.12 build

Author: ashawley

Diff for: build.sbt

@@ -33,7 +33,7 @@ lazy val xml = crossProject.in(file("."))
       OsgiKeys.exportPackage := Seq(s"scala.xml.*;version=${version.value}"),
       libraryDependencies += "junit" % "junit" % "4.11" % "test",
       libraryDependencies += "com.novocode" % "junit-interface" % "0.10" % "test",
-      libraryDependencies += "org.scalacheck" %% "scalacheck" % "1.13.2" % "test",
+      libraryDependencies += "org.scalacheck" %% "scalacheck" % "1.13.4" % "test",
       libraryDependencies += ("org.scala-lang" % "scala-compiler" % scalaVersion.value % "test").exclude("org.scala-lang.modules", s"scala-xml*"),
       mimaPreviousVersion := Some("1.0.6"),
       // You cannot disable JVM test forking when working on scala modules