The call to sleep(1) inside of the enrollment loop caused a crash
on at least the etes603 driver.
Because in fp_enroll_finger_img the function enters an event
handling loop. This loop needs to start before the next libusb
event timeout. Which would not happen in the etes603 driver
because the timeout there was set to 1 second as well.
The basic model is that image drivers declare a fp_img_driver structure
rather than a fp_driver struct. fp_img_driver will contain primitive imaging
operations such as 'scan finger and return image'. The imgdev layer will
generically implement the primitive fp_driver operations, and the imgdev
layer will fix up the enroll/verify/etc pointers at driver registration
time.
Removed const from all fp_driver declarations, as these are now modified
dynamically in the case of imaging drivers.
Prints can now be saved to disk (but you currently must classify which
finger they are) and you can load them later.
Added 2 simple example programs to demonstrate this.
