Resolving ASKAPSDP-1598: Adding a patch to the Duchamp-1.6.1 3rdParty package. I've also checked this into the Duchamp trunk, and so it will form part of the next release.

git-svn-id: https://svn.atnf.csiro.au/askapsdp/trunk@6550 1db04d4c-0ff0-4329-ae0b-98c546476c6a