Add power management support

[akpm@osdl.org: cleanup]
Signed-off-by: NRodolfo Giometti <giometti@linux.it>
Signed-off-by: NAntonino Daplas <adaplas@pol.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>