Set surface title on platform window creation

When creating the platform window, the surface title should be set to
the value in the associated QWindow otherwise the compositor won't know
it until setWindowTitle() is called.

Change-Id: I5d0e16c78bf5dd7c9dde47254809d18cf77f0a82
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>