add detailed error values to block layer

I saw that the Adaptec RAID developers are in need of detailed IO error values too, so I wanted to post what I have so we can try to work together. I have converted the block layer, but have not finished the end request callers.

01-ec-core.patch just defines the error values, and modifies the request completion functions. Right now they just convert the uptodate status to an error value. Per Jeff's advice I did not define my own erronos. wrt his other comment, I was not sure if wanted me to print the error value in string form in __end_that_request, or just print the numerical value.

02-ec-bioendio.patch converts the bio_endio and bi_end_io callers to pass one of the error values defined above instead of the -Exxx.

Both patches were built against 2.6.5-rc1.

The block layer error values are not too exciting. There were very few drivers that did not just return EIO. The end request users will be much more fun :)

Thanks,

Mike Chrisite