* doc/scanimage.man doc/saned.man: updated description of password
file
* sanei/sanei_auth.c frontend/saned.c frontend/scanimage.c: replaced
index() by strchr(). Changed style of password file
* backend/net.c: the net backend now prepends net:host: to the
resource before calling the auth_callback function
* lib/md5.c include/md5.h: added md5 functions from GNU textutils
* include/sane/sanei_auth.h sanei/sanei_auth.c: implemented new
SANE interface for user authorization using MD5 digest