perf tools: Add trace-event object

perf tools: Add trace-event object

Add trace-event object to keep together 'struct pevent' object with its
loaded plugins with following interface:

int trace_event__init(struct trace_event *t);

  - Initalizes 'struct pevent' object and loads plugins for it

void trace_event__cleanup(struct trace_event *t);

  - Cleanups both 'struct pevent' and plugins

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.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/1386076182-14484-10-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>