oprofile i386 arch updates, including some internal API changes and support
for stack trace sampling.

(akpm: I added a nasty hack to fix the x86_64 build.  However the feature is
untested on x86_64 and probably doesn't work yet).
Signed-off-by: John Levon <levon@movementarian.org>
Signed-off-by: Greg Banks <gnb@melbourne.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>