Behaviors of socket class waitFor*() inconsistent

[Note: Re-raised from QT-1185, originally reported by Oswald Buddenhagen]

In QLocalSocket, on windows, waitForReadyRead() will not return soon when the socket was already disconnected.

On unix, it will return false even if buffered data is still available after it was disconnected (i would expect this to be possible unless the disconnected state is not entered until all data was read - the docs unfortunately do not say anything about synchronization of read and disconnect, unlike write and disconnect).

On unix, waitForDisconnected() will complain when already disconnected, on windows it won't (the former seems bogus to me).

I have checked only a few functions. i suggest a full audit in that regard of both QLocalSocket and QAbstractSocket.