Update dpkg's Breaks dependency to include dpkg-dev (<< 1.15.8)

It ensures that older versions of dpkg-dev that did not depend on
libdpkg-perl must be upgraded together with dpkg.

Reported-by: Lionel Elie Mamane <lionel@mamane.lu>

debian/changelog

@@ -22,6 +22,9 @@ dpkg (1.15.8.5) UNRELEASED; urgency=low
     tarballs. Upstream binary files modified by the packager were not properly
     installed due to this. Thanks to James Westby for the report.
     Closes: #594440
+  * Make dpkg Breaks: dpkg-dev (<< 1.15.8) so that older versions of dpkg-dev
+    that did not depend on libdpkg-perl must be upgraded together with dpkg.
+    Closes: #596417
 
   [ Helge Kreutzmann ]
   * Fix encoding of German addendum. Closes: #595643

debian/control

@@ -32,7 +32,7 @@ Architecture: any
 Essential: yes
 Pre-Depends: ${shlibs:Depends}, coreutils (>= 5.93-1), xz-utils
 Depends: ${misc:Depends}
-Breaks: dpkg-dev (<< 1.14.16), libdpkg-perl (<< 1.15.8),
+Breaks: dpkg-dev (<< 1.15.8), libdpkg-perl (<< 1.15.8),
  apt (<< 0.7.7), aptitude (<< 0.4.7-1),
 # install-info transition
 # see http://wiki.debian.org/Transitions/DpkgToGnuInstallInfo