perf report: Use properly build_id kernel binaries

If we bring the recorded perf data together with kernel binary from another
machine using:

	on server A:
	perf archive

	on server B:
	tar xjvf perf.data.tar.bz2 -C ~/.debug

the build_id kernel dso is not properly recognized during the "perf report"
command on server B.

The reason is, that build_id dsos are added during the session initialization,
while the kernel maps are created during the sample event processing.

The machine__create_kernel_maps functions ends up creating new dso object for
kernel, but it does not check if we already have one added by build_id
processing.

Also the build_id reading ABI quirk added in commit:

 - commit b2511481


   perf build-id: Add quirk to deal with perf.data file format breakage

populates the "struct build_id_event::pid" with 0, which
is later interpreted as DEFAULT_GUEST_KERNEL_ID.

This is not always correct, so it's better to guess the pid
value based on the "struct build_id_event::header::misc" value.

- Tested with data generated on x86 kernel version v2.6.34
  and reported back on x86_64 current kernel.
- Not tested for guest kernel case.

Note the problem stays for PERF_RECORD_MMAP events recorded by perf that
does not use proper pid (HOST_KERNEL_ID/DEFAULT_GUEST_KERNEL_ID). They are
misinterpreted within the current perf code. Probably there's not much we
can do about that.

Cc: Avi Kivity <avi@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Link: http://lkml.kernel.org/r/20110601194346.GB1934@jolsa.brq.redhat.com
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>