Enable Ubuntu 16.04 build at packager.io (#3617)

.pkgr.yml

@@ -7,10 +7,15 @@ targets:
       - git
   debian-8:
     <<: *debian
+  ubuntu-12.04:
+    <<: *debian
   ubuntu-14.04:
     <<: *debian
-  ubuntu-12.04:
+  ubuntu-16.04:
     <<: *debian
+    build_dependencies:
+      - bzr
+      - mercurial
   centos-6: &el
     build_dependencies:
       - pam-devel