And use its emulated_interface. This adds a private_refcount to track
hidden references, and a reference to the wined3d_device, to keep the
d3d_device alive while not publicly referencing it.

This uses d3d_device_context_state_AddRef on init so that the initial
references are also traced, making it easier to verify that nothing is
leaked.
Signed-off-by: Rémi Bernon <rbernon@codeweavers.com>
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>