perf: Add a sample_event type to the event_union

Add a sample_event type to the event_union so that raw samples can
be processed easily.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20090912130511.411434b5@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>