perf tools: Add prelink suggestion to dso update message

Following a prelink run mapped files for long running processes can show
as deleted. The current message suggests restarting long running
processes. Add to that a suggestion that prelink might be the cause.

Old message:
/lib64/libc-2.14.so was updated, restart the long running
 apps that use it!

New message:
/lib64/libc-2.14.so was updated (is prelink enabled?).
  Restart the long running apps that use it!

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1318985085-20776-1-git-send-email-dsahern@gmail.com
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>