replace unicode arrows

* ⇒, →, ←
* because we don't want to show them in documentation snippets and
  then it's complicated to avoid that when snippets are
  located in src/test/scala in individual modules
* dont replace object `→` in FSM.scala and PersistentFSM.scala

akka-docs/src/test/scala/docs/io/ScalaUdpMulticastSpec.scala

@@ -20,7 +20,7 @@ class ScalaUdpMulticastSpec extends TestKit(ActorSystem("ScalaUdpMulticastSpec")
   "listener" should {
     "send message back to sink" in {
       val ipv6ifaces =
-        NetworkInterface.getNetworkInterfaces.asScala.toSeq.filter(iface ⇒
+        NetworkInterface.getNetworkInterfaces.asScala.toSeq.filter(iface =>
           iface.supportsMulticast &&
             iface.isUp &&
             iface.getInetAddresses.asScala.exists(_.isInstanceOf[Inet6Address]))
@@ -33,7 +33,7 @@ class ScalaUdpMulticastSpec extends TestKit(ActorSystem("ScalaUdpMulticastSpec")
         // on the platform (awsdl0 can't be used on OSX, docker[0-9] can't be used in a docker machine etc.)
         // therefore: try hard to find an interface that _does_ work, and only fail if there was any potentially
         // working interfaces but all failed
-        ipv6ifaces.exists { ipv6iface ⇒
+        ipv6ifaces.exists { ipv6iface =>
           // host assigned link local multicast address http://tools.ietf.org/html/rfc3307#section-4.3.2
           // generate a random 32 bit multicast address with the high order bit set
           val randomAddress: String = (Random.nextInt().abs.toLong | (1L << 31)).toHexString.toUpperCase
@@ -51,7 +51,7 @@ class ScalaUdpMulticastSpec extends TestKit(ActorSystem("ScalaUdpMulticastSpec")
             true
 
           } catch {
-            case _: AssertionError ⇒
+            case _: AssertionError =>
               system.log.info("Failed to run test on interface {}", ipv6iface.getDisplayName)
               false