The core NLKD additions.

With other debugging code living scattered across the (official or
external) tree(s), this tries to atb once establish a common place
for debugging code in a new debug/ directory.

Note that this depends on the i386 cmpxchg adjustments patch, which
isn't in 2.6.14, but has supposedly been merged already into 2.6.15.

Signed-Off-By: Jan Beulich <jbeulich@novell.com>

(actual patch attached)