compilation fix for wxUSE_STL==1 build

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@49096 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/cppunit.h

@@ -95,7 +95,11 @@
 
 inline std::ostream& operator<<(std::ostream& o, const wxString& s)
 {
-    return o << (const char *)wxSafeConvertWX2MB(s);
+#if wxUSE_UNICODE
+    return o << (const char *)wxSafeConvertWX2MB(s.wc_str());
+#else
+    return o << s.c_str();
+#endif
 }