[PATCH] x86_64: Fix interaction of single stepping with debuggers

Ported from i386/Linus

Fix another TF corner case.  Need to do the special TF handling for all
signals to make debuggers happy

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