[qtwayland] Add an extension for sending keys to specific windows.
Merge pull request #31 from adenexter/master

[qtwayland] Add an extension for sending keys to specific windows.
Compositor: provide a way to update the clipboard on a client

Clipboard synchronization happens when a client is keyboard-focused, but
some clients may require clipboard access even when not in focus. Add
an updateSelection() slot to QWaylandSurface so that the compositor
implementor can synchronize the clipboard manually or through a
signal-slot connection.