gzip build and zlib strategy setting

Hi all, I've added a build for gzip which will apply my patch to stop the mtime being populated in the gz header. It builds against the current version of gzip in debian wheezy.

I've also added a patch to the dpkg build to always use the default strategy, and merged in vyrly's master with my patch to cause the dpkg build to fail if the zlib headers aren't installed.

Thanks,

Ben
(benbrown on freenode)