Extend diamond multi test to fix go

Examples/test-suite/multi_import.h

@@ -1,3 +1,11 @@
+#ifndef MULTI_IMPORT_H
+#define MULTI_IMPORT_H
+
+class WWW {
+  public:
+    void nullop() const {}
+};
+
 class XXX
 {
 	public:
@@ -15,3 +23,5 @@ class ZZZ : public XXX
 	public:
 		int testz() { return 2;}
 };
+
+#endif /* MULTI_IMPORT_H */

Examples/test-suite/multi_import_a.i

@@ -14,3 +14,7 @@ class ZZZ : public XXX
 public:
    int testz();
 };
+
+%inline %{
+void use_www_a(const WWW& w) {w.nullop();}
+%}

Examples/test-suite/multi_import_b.i

@@ -11,3 +11,7 @@ class YYY : public XXX
 public:
         int testy();
 };
+
+%inline %{
+void use_www_b(const WWW& w) {w.nullop();}
+%}

Examples/test-suite/multi_import_c.i

@@ -1,5 +1,8 @@
 %import "multi_import_d.i"
 
+// NB: this module is only imported, never compiled, so it's not necessary to
+// include the header for testing purposes.
+
 class XXX
 {
 public:

Examples/test-suite/multi_import_d.i

@@ -1,3 +1,12 @@
 %module multi_import_d
 
 %constant int myval = 1234;
+
+%{
+#include "multi_import.h"
+%}
+
+class WWW {
+  public:
+    void nullop() const;
+};