Instead of trying to show the current loop by naively looking for the
next backward jump, just use 'j' to toggle showing arrows connecting
jump with its target.

And do it for forward jumps as well.

Loop detection requires more code to follow the flow control, etc.
Reported-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-soahcn1lz2u4wxj31ch0594j@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>