Various scala-2.13.0-M5 fixes

Clearer imports in TcpDnsClient

Accept SVG's when checking if diagrams were generated

Fix akka-actor MiMa issues

akka-testkit scalafix changes

Update scalatest to 2.13-released snapshot

akka-stream scalafix changes

Update ssl-config

To version that's released with -M5

Take elements directly out of buffer

Manually fix immutable.Seq / Doc link

Make sure the right Concat, Sink is imported

akka-stream binary compat

akka-stream-testkit scalafix

akka-actor-tests scalafix

Eta-expensions

akka-testkit/src/main/scala/akka/testkit/CallingThreadDispatcher.scala

@@ -50,7 +50,7 @@ private[testkit] class CallingThreadDispatcherQueues extends Extension {
 
   // we have to forget about long-gone threads sometime
   private def gc(): Unit = {
-    queues = (Map.newBuilder[CallingThreadMailbox, Set[WeakReference[MessageQueue]]] /: queues) {
+    queues = queues.foldLeft(Map.newBuilder[CallingThreadMailbox, Set[WeakReference[MessageQueue]]]) {
       case (m, (k, v)) ⇒
         val nv = v filter (_.get ne null)
         if (nv.isEmpty) m else m += (k → nv)