Bump version to 1.18.15

debian/changelog

@@ -1,3 +1,9 @@
+dpkg (1.18.15) UNRELEASED; urgency=medium
+
+  *
+
+ -- Guillem Jover <guillem@debian.org>  Fri, 11 Nov 2016 03:40:42 +0100
+
 dpkg (1.18.14) unstable; urgency=medium
 
   [ Guillem Jover ]