debian: Name each public-domain license with a different name

debian/changelog

@@ -83,6 +83,7 @@ dpkg (1.18.0) UNRELEASED; urgency=low
     - Remove old trigger related Breaks and Conflicts from dpkg.
     - Only use stackprotectorstrong when building dpkg with gcc >= 4.9.
     - Switch to debhelper compatibility level 9.
+    - Name each public-domain license with a different name.
   * Documentation:
     - Document arch-qualifiers for dependency fields in deb-control(5) and
       deb-src-control(5). Reported by Johannes Schauer <j.schauer@email.de>.

debian/copyright

@@ -100,7 +100,7 @@ Copyright:
  Copyright © 2009 Chris Coulson <chrisccoulson@googlemail.com>
  Copyright © 2012 Carsten Hey <carsten@debian.org>
  Copyright © 2014 Nir Soffer <nirs@hyperms.com>
-License: public-domain
+License: public-domain-s-s-d
  Written by Marek Michalkiewicz <marekm@i17linuxb.ists.pwr.wroc.pl>,
  public domain.  Based conceptually on start-stop-daemon.pl, by Ian
  Jackson <ijackson@gnu.ai.mit.edu>.  May be used and distributed
@@ -116,7 +116,7 @@ License: public-domain
 Files: lib/compat/md5.*
 Copyright:
  Copyright © 1993 Colin Plumb
-License: public-domain
+License: public-domain-md5
  This code implements the MD5 message-digest algorithm.
  The algorithm is due to Ron Rivest.  This code was
  written by Colin Plumb in 1993, no copyright is claimed.