perf tools: Add sort__has_comm variable

The sort__has_comm variable is to check whether the comm sort key is
given.  This is necessary to support thread filtering in the TUI hists
browser later.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1457533253-21419-1-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/sort.h b/tools/perf/util/sort.h
index 151afc1..3f4e359 100644
--- a/tools/perf/util/sort.h
+++ b/tools/perf/util/sort.h
@@ -37,6 +37,7 @@
 extern int sort__has_sym;
 extern int sort__has_socket;
 extern int sort__has_thread;
+extern int sort__has_comm;
 extern enum sort_mode sort__mode;
 extern struct sort_entry sort_comm;
 extern struct sort_entry sort_dso;