Use the same approach of GTask, making possible to set the data from a
function. Givent the fact that a SSM has now a device parameter, it's
generally not needed to pass an extra data value.
In such case make it possible to set it and to define a destroy-notify
function to handle its destruction when freeing the SSM.
As the driver is not a normal image device, we need to add a custom
script to test it. Note that the ioctl dump must also be manually
modified unfortunately as the state is tracked incorrectly for the
device by umockdev-record.
This allows us to properly extract metadata for prints that are stored
on the device. We could for example delete the oldest prints first with
this information.
Heavily modified by Benjamin Berg <bberg@redhat.com> to port it to the
new libfprint API and adjust the coding style to follow more closely
other drivers.
