perf evlist: Rename __group method to __set_leader

Just like was done for parse_events__set_leader.

Also we need to have the list_entry set_leader method in evlist.c so that we
don't grow another dep in the python binding:

 # ~acme/git/linux/tools/perf/python/twatch.py
 Traceback (most recent call last):
   File "/home/acme/git/linux/tools/perf/python/twatch.py", line 16, in <module>
     import perf
 ImportError: /home/acme/git/build/perf/python/perf.so: undefined symbol: parse_events__set_leader

And also remove a pr_debug from evsel.c so that we avoid this one too:

 # ~acme/git/linux/tools/perf/python/twatch.py
 Traceback (most recent call last):
   File "/home/acme/git/linux/tools/perf/python/twatch.py", line 16, in <module>
     import perf
 ImportError: /home/acme/git/build/perf/python/perf.so: undefined symbol: eprintf

Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-0hk9dazg9pora9jylkqngovm@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index a19ccd7..7fe677e 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -118,6 +118,9 @@
 void perf_evlist__delete_maps(struct perf_evlist *evlist);
 int perf_evlist__set_filters(struct perf_evlist *evlist);
 
+void __perf_evlist__set_leader(struct list_head *list);
+void perf_evlist__set_leader(struct perf_evlist *evlist);
+
 u64 perf_evlist__sample_type(const struct perf_evlist *evlist);
 bool perf_evlist__sample_id_all(const const struct perf_evlist *evlist);
 u16 perf_evlist__id_hdr_size(const struct perf_evlist *evlist);
@@ -131,6 +134,4 @@
 void perf_evlist__splice_list_tail(struct perf_evlist *evlist,
 				   struct list_head *list,
 				   int nr_entries);
-
-void perf_evlist__group(struct perf_evlist *evlist);
 #endif /* __PERF_EVLIST_H */