[PATCH] scsi_debug in 2.5.64

Here is a second attempt to patch scsi_debug in
2.5.64 . My reference version was out of sync in
my previous posting.

Changelog:
   - add recovered error injection (this is a bit
     different to the patch proposed by Kurt Garloff)
   - fix flakiness in scsi_cmnd::result when errors
     are being injected
   - fix medium error injection
   - make "every_nth" writeable in sysfs
   - small re-arrangement of error flags in "opts"
   - clean up some of the naming

Updated http://www.torque.net/sg/sdebug25.html

This patch does not include Mike Anderson's sysfs
probe() cleanup.

In 2.5.64 scsi error handling is flaky and sysfs is
especially flaky in 2.5.64-bk3. I'll send some finding
to the list when things stabilize a bit. [For anyone
who is bored, try following the tortured sequence
of scsi commands generated by the block/sd/mid-level
layers in response to a persistent medium error.]