Add option to dump symbols found in events.

e.g., perf script -f comm,pid,tid,time,trace,sym

swapper     0/0       537.037184: prev_comm=swapper prev_pid=0 prev_prio=120...
        ffffffff81030350 perf_trace_sched_switch ([kernel.kallsyms])
        ffffffff81382ac5 schedule ([kernel.kallsyms])
        ffffffff8100134a cpu_idle ([kernel.kallsyms])
        ffffffff81370b39 rest_init ([kernel.kallsyms])
        ffffffff81696c23 start_kernel ([kernel.kallsyms].init.text)
        ffffffff816962af x86_64_start_reservations ([kernel.kallsyms].init.text)
        ffffffff816963b9 x86_64_start_kernel ([kernel.kallsyms].init.text)

sshd  1675/1675    537.037309: prev_comm=sshd prev_pid=1675 prev_prio=120...
        ffffffff81030350 perf_trace_sched_switch ([kernel.kallsyms])
        ffffffff81382ac5 schedule ([kernel.kallsyms])
        ffffffff813837aa schedule_hrtimeout_range_clock ([kernel.kallsyms])
        ffffffff81383886 schedule_hrtimeout_range ([kernel.kallsyms])
        ffffffff8110c4f9 poll_schedule_timeout ([kernel.kallsyms])
        ffffffff8110cd20 do_select ([kernel.kallsyms])
        ffffffff8110ced8 core_sys_select ([kernel.kallsyms])
        ffffffff8110d00d sys_select ([kernel.kallsyms])
        ffffffff81002bc2 system_call ([kernel.kallsyms])
            7f1647e56e93 __GI_select (/lib64/libc-2.12.90.so)

netstat  1692/1692    537.038664: prev_comm=netstat prev_pid=1692 prev_prio=...
        ffffffff81030350 perf_trace_sched_switch ([kernel.kallsyms])
        ffffffff81382ac5 schedule ([kernel.kallsyms])
        ffffffff81002c3a sysret_careful ([kernel.kallsyms])
            7f7a6cd1b210 __GI___libc_read (/lib64/libc-2.12.90.so)
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <1299734608-5223-6-git-send-email-daahern@cisco.com>
Signed-off-by: NDavid Ahern <daahern@cisco.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>