Add dummy changelog entry for Tails 1.2.1.

debian/changelog

+tails (1.2.1) UNRELEASED; urgency=low
+
+  * Dummy changelog entry for next point release.
+
+ -- Tails developers <tails@boum.org>  Fri, 17 Oct 2014 01:46:05 +0200
+
 tails (1.2) unstable; urgency=medium
 
   * Major new features