Fix directorin SWIGTYPE typemaps to make a copy as these are used for pass by value.

Closes #434

Examples/test-suite/csharp/director_pass_by_value_runme.cs

@@ -0,0 +1,43 @@
+using System;
+using director_pass_by_valueNamespace;
+
+public class runme
+{
+  private static void WaitForGC()
+  {
+    System.GC.Collect();
+    System.GC.WaitForPendingFinalizers();
+    System.Threading.Thread.Sleep(10);
+  }
+
+  static void Main()
+  {
+    runme r = new runme();
+    r.run();
+  }
+
+  void run()
+  {
+    Caller caller = new Caller();
+    caller.call_virtualMethod(new director_pass_by_value_Derived());
+    {
+      int countdown = 5;
+      while (true) {
+        WaitForGC();
+        if (--countdown == 0)
+          break;
+      };
+    }
+    // bug was the passByVal 'global' object was destroyed after the call to virtualMethod had finished.
+    int ret = runme.passByVal.getVal();
+    if (ret != 0x12345678)
+      throw new Exception("Bad return value, got " + ret.ToString("x"));
+  }
+  public static PassedByValue passByVal;
+}
+
+class director_pass_by_value_Derived : DirectorPassByValueAbstractBase {
+  public override void virtualMethod(PassedByValue pbv) {
+    runme.passByVal = pbv;
+  }
+}