Doxygen: Add link to the bug report.

svn path=/nixpkgs/trunk/; revision=32677

pkgs/top-level/all-packages.nix

@@ -3007,11 +3007,8 @@ let
 
   doxygen = lowPrio (doxygen_gui.override { qt4 = null; });
 
-  /* XXX: The LaTeX output with Doxygen 1.8.0 makes LaTeX barf:
-
-       ! You can't use `\/' in vertical mode.
-
-     Thus, keep 1.7 around until a better fix is available.  */
+  /* XXX: The LaTeX output with Doxygen 1.8.0 makes LaTeX barf.
+     See <https://bugzilla.gnome.org/show_bug.cgi?id=670973>.  */
   doxygen_1_7 = callPackage ../development/tools/documentation/doxygen/1.7.nix {
     qt4 = null;
   };