QtRO should use the abstract namespace option for QLocalSocket/Server when using the local backend on Linux

Fix for https://bugreports.qt.io/browse/QTBUG-16090 introduces an option (AbstractNamespaceOption) allowing using abstract namespaces for QLocalSocket/QLocalServer classes. 

Currently, QtRO, for urls starting from "local:", uses the generic sockets which rely on creating temporary files. 

In some secured Linux systems (chrooted environment, cgroup, nfs and so on) there is no writable places at all. So some Qt programs does not work. For instance, communication between Android activity and service within the same app using RO with "local:*" url is not possible.

Therefore, I think that using AbstractNamespaceOption for QLocalSocket/QLocalServer in RO's local backend implemention should be considered.