Common base class for all Qt socket classes

Currently, QLocalSocket inherits from QIODevice and QTcpSocket inherits from QAbstractSocket. It would be beneficial to have these classes (and other socket classes) inherit from the same base class in order to allow switching between the two socket types transparently without requiring much to change in the client code.

The comments in this blog post (http://blog.qt.digia.com/2008/02/22/qlocalserver-qlocalsocket/) seemed to indicate that the plan was for this to be done for Qt 5, however it's not clear to me if this is being worked on. Several people have expressed interest in this, and it seems that getting this in on time for Qt 5 is important, as we now have the ability to break binary compatibility.