Allowing symbolic events processing to report back error.

  $ perf record -e 'cycles/period=krava/' ls
  event syntax error: '../period=krava/'
                                 \___ expected numeric value

  $ perf record -e 'cycles/name=1/' ls
  event syntax error: '..es/name=1/'
                                 \___ expected string value
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1429729824-13932-10-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>