yet more udev/hotplug changes

[Bill Nottingham]

Beginning tomorrow, hotplug events will now be handled directly by udev
for the:

- firmware
- scsi
- ieee1394

subsystems.

The only hotplug agents left will be input (because the kernel isn't fixed
yet) and net (because that's, well, different).

Removed but not replaced were the dasd/tape s390 agents; these just created
additional device symlinks for compatibility with really really old devfs
installations; it's probably time for this compatiblity to be removed.

Bill