debian: Add Breaks on man-db, fontconfig and readahead-fedora

The old versions of these packages produced trigger cycles as they
were using awaiting trigger directives.

Closes: #768599

debian/changelog

@@ -8,6 +8,8 @@ dpkg (1.17.22) UNRELEASED; urgency=low
     compatibility symlinks under /usr/sbin/. There are still packages
     using those paths, but the relevant lintian check did not list any,
     so this got removed prematurely.
+  * Add Breaks on old man-db, fontconfig and readahead-fedora packages using
+    awaiting triggers, as they produce trigger cycles. Closes: #768599
 
   [ Updated programs translations ]
   * German (Sven Joachim).

debian/control

@@ -36,6 +36,10 @@ Essential: yes
 Pre-Depends: ${shlibs:Depends}, tar (>= 1.23)
 Depends: ${misc:Depends}
 Breaks: dpkg-dev (<< 1.15.8), libdpkg-perl (<< 1.15.8),
+# These cause trigger cycles due to using awaiting trigger directives.
+ man-db (<< 2.6.3-6), fontconfig (<< 2.11.0-6.2),
+ readahead-fedora (<< 2:1.5.6-5.2),
+# These do not support triggers.
  apt (<< 0.7.7), aptitude (<< 0.4.7-1)
 Conflicts:
 # The following Conflicts against removed packages using install-info