Fix missing returns in the Doxygen test suite code.

Missing returns resulted in test suite failures now that it is built with
-Wreturn-type, so avoid them by simply making most of the functions void and
adding explicit return statements to a couple of them that used Doxygen
\return command in their documentation, which doesn't make sense for the void
functions.

Examples/test-suite/doxygen_translate_links.i

@@ -44,7 +44,7 @@ public:
  * \sa superFunc()
  *
  */
-int function()
+void function()
 {
 }