perf record: Mention paranoid sysctl when failing to create counter

[acme@mica linux-2.6-tip]$ perf record -a -f
   Fatal: Permission error - are you root?
 	 Consider tweaking /proc/sys/kernel/perf_event_paranoid.

 [acme@mica linux-2.6-tip]$

Suggested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1268333592-30872-2-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>