o The device is now specified by the DEVPATH in the environment,
it's no longer needed to pass the major/minor to the callout.
o leading spaces and slashes are now removed from the returned string
and spaces are replaced by underscore, to not to confuse udev.
o Arnd Bergmann <arnd@arndb.de> provided the code to recognize s390
dasd disk labels. The -d switch tries to read the main block device
instead of the partition.