perf script: Add period as a default output column

Adding period as a default output column in script command fo hardware,
software and raw events.

If PERF_SAMPLE_PERIOD sample type is defined in perf.data, following
will be displayed in perf script output:

  $ perf script
              ls  8034 57477.887209:     250000 task-clock:  ffffffff81361d72 memset ([kernel.kallsyms])
              ls  8034 57477.887464:     250000 task-clock:  ffffffff816f6d92 _raw_spin_unlock_irqrestore ([kernel.kallsyms])
              ls  8034 57477.887708:     250000 task-clock:  ffffffff811a94f0 do_munmap ([kernel.kallsyms])
              ls  8034 57477.887959:     250000 task-clock:        34080916c6 get_next_seq (/usr/lib64/libc-2.17.so)
              ls  8034 57477.888208:     250000 task-clock:        3408079230 _IO_doallocbuf (/usr/lib64/libc-2.17.so)
              ls  8034 57477.888717:     250000 task-clock:  ffffffff814242c8 n_tty_write ([kernel.kallsyms])
              ls  8034 57477.889285:     250000 task-clock:...