Bug#359178: lintian: fails to detect duplicate build dep

[Justin Pryzby <justinpryzby@users.sourceforge.net>]

Package: lintian
Version: 1.23.15
Severity: wishlist

Please detect duplicate build-dependency relation, as in the current
links2 package:

Build-Depends: debhelper (>= 4.0.0), libpng12-dev | libpng3-dev,
libtiff4-dev, libjpeg62-dev, libx11-dev, libgpmg1-dev [i386 ia64 alpha
                             ^^^^^^^^^^
amd64 arm hppa m32r m68k mips mipsel powerpc ppc64 s390 s390x sh3
sh3eb sh4 sh4eb sparc], type-handling (>= 0.2.1), libsvga1-dev [i386
amd64], libdirectfb-dev, libx11-dev, x-dev
                         ^^^^^^^^^^

Same for tktable:

Build-Depends: debhelper (>> 4.0.0), tcl8.4, tcl8.4-dev, tk8.4,
               ^^^^^^^^^^^^^^^^^^^^^
tk8.4-dev, rman, debhelper
	         ^^^^^^^^^