%interface family of macros no longer add variable wrappers

The getter/setter methods used for wrapping methods are no longer
added to the interface class.

Closes #1524

Also add in testcase for enums.

Examples/test-suite/csharp/multiple_inheritance_interfaces_runme.cs

@@ -83,5 +83,7 @@ public class multiple_inheritance_interfaces_runme {
     d.ia(10);
     d.ia("bye");
     d.ia("bye", false);
+
+    UndesirablesSwigImpl.UndesiredStaticMethod(UndesirablesSwigImpl.UndesiredEnum.UndesiredEnum1);
   }
 }