perf_counter tools: Merge common code into perfcounters.h

kerneltop's MAX_COUNTERS is increased from 8 to 64(the value used by perfstat).

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --cc Documentation/perf_counter/kerneltop.c
Simple merge

diff --cc Documentation/perf_counter/perfcounters.h
Simple merge

diff --cc Documentation/perf_counter/perfstat.c
Simple merge