Allowing storing stat record data into pipe, so report tools
(report/script) could read data directly from record.

Committer note:

Before this patch:

  $ perf stat record -o - usleep 1 | perf report -i -
  incompatible file format (rerun with -v to learn more)
  $ perf stat record -o - usleep 1 | perf script -i -
  incompatible file format (rerun with -v to learn more)
  $ ls -la perf.data
  ls: cannot access perf.data: No such file or directory
  $

After:

  $ perf stat record -o - usleep 1 | perf report -i -
  # To display the perf.data header info, please use
  # --header/--header-only options.
  #
  Error:
  The - file has no samples!
  $ perf stat record -o - usleep 1 | perf script -i -
  Display of symbols requested but neither sample IP nor sample address
  is selected. Hence, no addresses to convert to symbols.
  0 [0x80]: failed to process type: 64
  $ ls -la perf.data
  ls: cannot access perf.data: No such file or directory
  $
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Kan Liang <kan.liang@intel.com>
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/1446734469-11352-7-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>