This drops the trace.info file and move its contents into the
common perf.data file.

This is done by creating a new trace_info section into this file. A
user of perf headers needs to call perf_header__set_trace_info() to
save the trace meta informations into the perf.data file.

A file created by perf after his patch is unsupported by previous
version because the size of the headers have increased.

That said, it's two new fields that have been added in the end of
the headers, and those could be ignored by previous versions if
they just handled the dynamic header size and then ignore the
unknow part. The offsets guarantee the compatibility. We'll do a
-stable fix for that.

But current previous versions handle the header size using its
static size, not dynamic, then it's not backward compatible with
trace records.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20091006213643.GA5343@nowhere>
Signed-off-by: Ingo Molnar <mingo@elte.hu>