perf_counter: output objects

Provide a {type,size} header for each output entry.

This should provide extensible output, and the ability to mix multiple streams.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Orig-LKML-Reference: <20090325113316.831607932@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>