* backend/artec.c: Added code in sane_exit() to free memory
malloced in sane_get_devices(). Declared several functions
'static' so they are not exported.
* TODO: removed 'artec' backend from list mentioned in describing
above problems.
* backend/artec.c: Fixed bug causing possible dereference of a NULL
pointer.
* backend/artec.desc: Modified USB entry to say AS6E scanner supported
by SANE AS6E backend.