T[ed]4 prefetch.

check for SSE bit instead of MMX, as pshufw was introduces in PIII, minor
optimization, typos...

256 byte S-box. AES_cbc_encrypt needs further work as it should also use
slow routines when processing smaller amount of data.

strong impact on decrypt performance, 20-25%. One probably should consider
switching between slower and faster routines depending on how much data
we were asked to process.

only chance for T[ed]4 to get evicted in this module is when its cache
"overlaps" with last 128 bits of key schedule.

prefetch could have been moved closer to Td4 references. Something for
later consideration...

debugging and doesn't affect functionality.

Submitted by: David Mosberger

Obtained from: http://www.hpl.hp.com/research/linux/crypto/