tools lib traceevent: Handle dynamic array's element size properly

Fixing the dynamic array format field parsing.

Currently the event_read_fields function could segfault while parsing
dynamic array other than string type. The reason is the event->pevent
does not need to be set and gets dereferenced unconditionaly.

Also adding proper initialization of field->elementsize based on the
parsed dynamic type.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1359060403-32422-1-git-send-email-jolsa@redhat.com


[ committer note: Made a char pointer parameter const, as requested by Steven ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>