Add an early exception handler on x86-64 to get better debugging output for
crashes before traps_init. 

Requires earlyconsole.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>