qdbusxml2cpp: generate "using" rather than "typedef"

It's more modern :)

I was hoping it would allow to forward declare the org::kde::Foo class,
but unfortunately it doesn't, the forward declaration has to use
"using" or "typedef" too...

Change-Id: I9ec2900ac25c1bca75d097aa339fd2a872568f95
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/tools/qdbusxml2cpp/qdbusxml2cpp.cpp

@@ -707,8 +707,8 @@ static void writeProxy(const QString &filename, const QDBusIntrospection::Interf
             // add this class:
             if (!name.isEmpty()) {
                 hs << QString(current.count() * 2, QLatin1Char(' '))
-                   << "typedef ::" << classNameForInterface(it->constData()->name, Proxy)
-                   << " " << name << ";" << Qt::endl;
+                   << "using " << name << " = ::" << classNameForInterface(it->constData()->name, Proxy)
+                   << ";" << Qt::endl;
             }
 
             if (it == interfaces.constEnd())