perf stat report: Add support to initialize aggr_map from file

perf stat report: Add support to initialize aggr_map from file

Using perf.data's perf_env data to initialize aggregate config.

Reported-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1446734469-11352-15-git-send-email-jolsa@kernel.org
[ s/stat/st/g, s/socket/socket_id/g to fix 'already defined' build error with older distros (e.g. RHEL6.7) ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>