Bump version to 1.18.6

debian/changelog

@@ -1,3 +1,9 @@
+dpkg (1.18.6) UNRELEASED; urgency=medium
+
+  *
+
+ -- Guillem Jover <guillem@debian.org>  Mon, 02 May 2016 05:35:24 +0200
+
 dpkg (1.18.5) unstable; urgency=medium
 
   [ Guillem Jover ]