Some things were odd with regard to the ownership of passed objects. Try
to make things sane overall, in particular with the possible floating
FpPrint reference.
Continuing an enroll was broken in case of a retry error. Explicitly add
code to wait for the finger to go OFF after a retry error, and ensure
that the enroll will continue once that has happened.
We prefixed them with fp- which is not as obvious as fpi-. Also,
explicitly mark them as private and to be skipped in the GObject
Introspection annotatinos.
Warning: FPrint: (Signal)fp-image-device-state-changed: argument object: Unresolved type: 'FpiImageDeviceState'
In order to be able to test the private device code (used by drivers) we
need to have that split a part in a different .c file so that we can compile
it alone and link with it both the shared library and the test executables.
Redefine fp_image_device_get_instance_private for private usage, not to move
the private struct as part of FpDevice.
