perf trace: Add pagefault statistics

perf trace: Add pagefault statistics

'perf trace' can show summary of events using -S option. This commit
also reports number of major/minor pagefault events in this summary.

$ perf trace -s --pf all -- sleep 1

 Summary of events:

 sleep (18604), 275 events, 99.6%, 197 minfaults, 0.000 msec

   syscall            calls      min       avg       max      stddev
                               (msec)    (msec)    (msec)        (%)
   --------------- -------- --------- --------- ---------     ------
   read                   2     0.000     0.001     0.002    100.00%
   open                   3     0.004     0.005     0.007     21.13%
   close                  3     0.001     0.001     0.001      1.37%
   fstat                  3     0.001     0.002     0.002     10.66%
   mmap                   8     0.002     0.004     0.006     10.69%
   mprotect               4     0.003     0.005     0.008     24.68%
   munmap                 1     0.005     0.005     0.005      0.00%
   brk                    3     0.001     0.002     0.003     28.08%
   access                 3     0.002     0.003     0.005     24.48%
   nanosleep              1  1000.747  1000.747  1000.747      0.00%
   execve                 8     0.000     0.033     0.246     91.00%
   arch_prctl             1     0.001     0.001     0.001      0.00%

Signed-off-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1404842716-19190-1-git-send-email-stfomichev@yandex-team.ru
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>