Fix missing return value in doxygen test

Doc/Manual/Doxygen.html

@@ -281,7 +281,7 @@ For example, you could use
 
     @transferfull Command ignored, but anything here is still included.
  */
-int * Fantastic() { }
+int * Fantastic();
 </pre></div>
 
 <p>

Examples/test-suite/doxygen_ignore.i

@@ -36,6 +36,6 @@
 
     @compileroptions This function must be compiled with /EHa when using MSVC.
  */
-int * func() { }
+int * func() { return 0; }
 
 %}