perf annotate browser: Use -> to navigate on assembly lines

perf annotate browser: Use -> to navigate on assembly lines

And add better explanations when the line isn't actionable, like non
assembly lines and on other instructions.

Suggested-by: Ingo Molnar <mingo@elte.hu>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
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-375n844b5wra7lgq08ou153j@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>