Added package HPLIP for printing to HP printers

HPLIP (Hewlett-Packard Linux Imaging & Printing) is an HP-developed solution
for printing, scanning, and faxing with HP inkjet and laser based printers
in Linux.

[Peter: fix Config.in white space]
Signed-off-by: Olivier Schonken <olivier.schonken@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>