perf session: Use evlist/evsel for managing perf.data attributes

So that we can reuse things like the id to attr lookup routine
(perf_evlist__id2evsel) that uses a hash table instead of the linear
lookup done in the older perf_header_attr routines, etc.

Also to make evsels/evlist more pervasive an API, simplyfing using the
emerging perf lib.

cc: Arun Sharma <arun@sharma-home.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.h

@@ -49,12 +49,17 @@ struct perf_evsel {
 	struct perf_event_attr	attr;
 	char			*filter;
 	struct xyarray		*fd;
-	struct xyarray		*id;
+	struct xyarray		*sample_id;
+	u64			*id;
 	struct perf_counts	*counts;
 	int			idx;
+	int			ids;
 	struct hists		hists;
 	char			*name;
-	void			*priv;
+	union {
+		void		*priv;
+		off_t		id_offset;
+	};
 	struct cgroup_sel	*cgrp;
 };