CONFIG_GENERIC_BUG support.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NYoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>