build: update waf to version 2.0.27

Change-Id: I6a35992c1c9a5dd30b6e04a8993edfafb7f358fa
diff --git a/.waf-tools/sanitizers.py b/.waf-tools/sanitizers.py
index a8fe55d..c65d009 100644
--- a/.waf-tools/sanitizers.py
+++ b/.waf-tools/sanitizers.py
@@ -1,4 +1,4 @@
-# -*- Mode: python; py-indent-offset: 4; indent-tabs-mode: nil; coding: utf-8; -*-
+# Davide Pesavento (LIP6), 2016
 
 def options(opt):
     opt.add_option('--with-sanitizer', action='store', default='', dest='sanitizers',