perf trace: Simplify '--summary' output

The output of 'perf trace --summary' tries to be too cute with
formatting and makes it very hard to read.  Simplify it in the spirit of
"strace -c":

[penberg@localhost libtrading]$ perf trace -a --duration 10000 --summary -- sleep 1
^C
 Summary of events:

 dbus-daemon (555), 10 events, 0.0%, 0.000 msec

                                                    msec/call
   syscall            calls      min      avg      max stddev
   --------------- -------- -------- -------- -------- ------
   sendmsg                2    0.002    0.005    0.008  55.00
   recvmsg                2    0.002    0.003    0.005  44.00
   epoll_wait             1    0.000    0.000    0.000   0.00

 NetworkManager (667), 56 events, 0.0%, 0.000 msec

                                                    msec/call
   syscall            calls      min      avg      max stddev
   --------------- -------- -------- -------- -------- ------
   poll                   2    0.000    0.002    0.003 100.00
   sendmsg               10    0.004    0.007    0.016  15.41
   recvmsg               16    0.002    0.003    0.005   8.24

 zfs-fuse (669), 4 events, 0.0%, 0.000 msec

                                                    msec/call
   syscall            calls      min      avg      max stddev
   --------------- -------- -------- -------- -------- ------
   futex                  2    0.000    0.001    0.002 100.00

Signed-off-by: Pekka Enberg <penberg@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: http://lkml.kernel.org/r/1384267334-18953-1-git-send-email-penberg@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>