Using declarations, directors and overloaded methods

Language::unrollVirtualMethods was assuming that the using
declaration would only introduce one method. Fix this by adding
in all the overloaded methods from a base class.

Affects code generation in C# and Java, but I was not able
to construct a test that failed before this commit.

Examples/test-suite/csharp/director_using_member_scopes_runme.cs

@@ -0,0 +1,70 @@
+using System;
+
+namespace director_using_member_scopesNamespace {
+
+public class runme
+{
+  static void Main()
+  {
+    runme r = new runme();
+    r.run();
+  }
+
+  void run()
+  {
+    NativeWindowType nwt = new NativeWindowType();
+    {
+      MyApplicationContextSDL a = new MyApplicationContextSDL();
+
+      if (ApplicationContextBase.call_setWindowGrab(a, nwt, true) != 100)
+        throw new Exception("failed");
+
+      if (ApplicationContextSDL.call_setWindowGrab(a, nwt, true) != 100)
+        throw new Exception("failed");
+    }
+
+    {
+      MyACSDL a = new MyACSDL();
+
+      if (ACB.call_setWindowGrab(a, nwt, true) != 100)
+        throw new Exception("failed");
+      if (ACB.call_setWindowGrab(a, "hi", 0) != 200)
+        throw new Exception("failed");
+
+      if (ACSDL.call_setWindowGrab(a, nwt, true) != 100)
+        throw new Exception("failed");
+      if (ACSDL.call_setWindowGrab(a, "hi", 0) != 200)
+        throw new Exception("failed");
+    }
+  }
+}
+
+class MyApplicationContextSDL: ApplicationContextSDL
+{
+  public MyApplicationContextSDL() : base()
+  {
+  }
+
+  public override int setWindowGrab(NativeWindowType win, bool grab)
+  {
+    return 100;
+  }
+}
+
+class MyACSDL: ACSDL
+{
+  public MyACSDL() : base()
+  {
+  }
+
+  public override int setWindowGrab(NativeWindowType win, bool grab)
+  {
+    return 100;
+  }
+  public override int setWindowGrab(string s, int val)
+  {
+    return 200;
+  }
+}
+
+}