debian: Make upgrading from debian SID easier

Make sure the version number of this sourcepackage is higher than
the one found in Debian SID.

Change-Id: I838632e9e90378a03235c2aebd5bc9ed06627ec8
Reviewed-on: https://gerrit.osmocom.org/113
Tested-by: Jenkins Builder
Reviewed-by: Holger Freyther <holger@freyther.de>

debian/changelog

@@ -1,4 +1,10 @@
-openbsc (0.14.0) UNRELEASED; urgency=low
+openbsc (0.15.1) UNRELEASED; urgency=medium
+
+  * Move forward toward a new release.
+
+ -- Holger Hans Peter Freyther <holger@moiji-mobile.com>  Tue, 24 May 2016 23:14:31 +0200
+
+openbsc (0.14.0) unstable; urgency=low
 
   * New upstream tag and additional patches.