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/parse-events.y b/tools/perf/util/parse-events.y
index 084c35fc..66850f8 100644
--- a/tools/perf/util/parse-events.y
+++ b/tools/perf/util/parse-events.y
@@ -119,7 +119,7 @@
 {
 	struct list_head *list = $3;
 
-	parse_events__group($1, list);
+	parse_events__set_leader($1, list);
 	$$ = list;
 }
 |
@@ -127,7 +127,7 @@
 {
 	struct list_head *list = $2;
 
-	parse_events__group(NULL, list);
+	parse_events__set_leader(NULL, list);
 	$$ = list;
 }