This is the port of scanbuttond, an utility to monitor the various buttons
found on many modern scanners which are intended to trigger certain actions
like copying, faxing or mailing the scanned document.
This daemon queries the scanner button state several times per second via
libusb and if it detects that a button is pressed it runs a shell script with
the button number as an argument.

The supported scanner backends currently are: epson, niash, plustek, snapscan