tools lib traceevent: Implement '%' operation

The operation '%' is not implemented on event-parse.c, causing an error
when parsing events with '%' the operation in its printk format. For
example,

  # perf record -e sched:sched_deadline_yield ~/yield-test
    Warning: [sched:sched_deadline_yield] unknown op '%'
  ....
  # perf script
    Warning: [sched:sched_deadline_yield] unknown op '%'
        test  1641 [006]  3364.109319: sched:sched_deadline_yield: \
                        [FAILED TO PARSE] now=3364109314595        \
                        deadline=3364139295135 runtime=19975597

This patch implements the '%' operation. With this patch, we see the
correct output:

  # perf record -e sched:sched_deadline_yield ~/yield-test
    No Warning

  # perf script
        yield-test  4005 [001]  4623.650978: sched:sched_deadline_yield: \
                now=4623.650974050                                       \
                deadline=4623.680957364 remaining_runtime=19979611

Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
Link: http://lkml.kernel.org/r/5c96a395c56cea6d3d13d949051bdece86cc26e0.1456157869.git.bristot@redhat.com


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