perf tools: Use an accessor to read thread comm

As the thread comm is going to be implemented by way of a more
complicated data structure than just a pointer to a string from the
thread struct, convert the readers of comm to use an accessor instead of
accessing it directly.

The accessor will be later overriden to support an enhanced comm
implementation.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-wr683zwy94hmj4ibogmnv9ce@git.kernel.org
[ Rename thread__comm_curr() to thread__comm_str() ]
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
[ Fixed up some minor const pointer issues ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 4ebbb40..6561ad2 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -35,6 +35,7 @@
 
 int thread__set_comm(struct thread *self, const char *comm);
 int thread__comm_len(struct thread *self);
+const char *thread__comm_str(const struct thread *thread);
 void thread__insert_map(struct thread *self, struct map *map);
 int thread__fork(struct thread *self, struct thread *parent);
 size_t thread__fprintf(struct thread *thread, FILE *fp);