perf_counter tools: Rework the file format

Create a structured file format that includes the full
perf_counter_attr and all its relevant counter IDs so that
the reporting program has full information.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>