This patch adds a 'raid10' module which provides features similar to both
raid0 and raid1 in the one array.  Various combinations of layout are
supported.

This code is still "experimental", but appears to work.
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>