Add new generic hw event: ref-cycles, which maps to
PERF_HW_COUNT_REF_CPUCYCLES:

 $ perf stat -e ref-cycles ls
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1323559734-3488-5-git-send-email-eranian@google.comSigned-off-by: Ingo Molnar <mingo@elte.hu>