perf report: Add -F option to specify output fields

The -F/--fields option is to allow user setup output field in any
order.  It can receive any sort keys and following (hpp) fields:

  overhead, overhead_sys, overhead_us, sample and period

If guest profiling is enabled, overhead_guest_{sys,us} will be
available too.

The output fields also affect sort order unless you give -s/--sort
option.  And any keys specified on -s option, will also be added to
the output field list automatically.

  $ perf report -F sym,sample,overhead
  ...
  #                     Symbol       Samples  Overhead
  # ..........................  ............  ........
  #
    [.] __cxa_atexit                       2     2.50%
    [.] __libc_csu_init                    4     5.00%
    [.] __new_exitfn                       3     3.75%
    [.] _dl_check_map_versions             1     1.25%
    [.] _dl_name_match_p                   4     5.00%
    [.] _dl_setup_hash                     1     1.25%
    [.] _dl_sysdep_start                   1     1.25%
    [.] _init                              5     6.25%
    [.] _setjmp                            6     7.50%
    [.] a                                  8    10.00%
    [.] b                                  8    10.00%
    [.] brk                                1     1.25%
    [.] c                                  8    10.00%

Note that, the example output above is captured after applying next
patch which fixes sort/comparing behavior.

Requested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/1400480762-22852-12-git-send-email-namhyung@kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>

tools/perf/Documentation/perf-report.txt

@@ -107,6 +107,16 @@ OPTIONS
 	And default sort keys are changed to comm, dso_from, symbol_from, dso_to
 	and symbol_to, see '--branch-stack'.
 
+-F::
+--fields=::
+	Specify output field - multiple keys can be specified in CSV format.
+	Following fields are available:
+	overhead, overhead_sys, overhead_us, sample and period.
+	Also it can contain any sort key(s).
+
+	By default, every sort keys not specified in -F will be appended
+	automatically.
+
 -p::
 --parent=<regex>::
         A regex filter to identify parent. The parent is a caller of this