This adds configurable support for doublefault reporting on x86

add/remove: 0/3 grow/shrink: 0/1 up/down: 0/-13048 (-13048)
function                                     old     new   delta
cpu_init                                     846     786     -60
doublefault_fn                               188       -    -188
doublefault_stack                           4096       -   -4096
doublefault_tss                             8704       -   -8704
Signed-off-by: NMatt Mackall <mpm@selenic.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>