assorted fixes, autopkgtest rewrite

Included is a bunch of smaller and mostly self-explantory fixes, and a rewrite of the autopkgtest.

For the latter, their purpose in Debian is to test the installed binary package. I completely understand why you opted for 'build-needed' to make the upstream testsuite find everything where expected, but that option is only necessary in very specific cases (e.g. when the tests themselves are generated during build) and otherwise best avoided. My changes use a simple but effective trick to make the upstream testsuite work without the need for a build or patches: symlink the utils into place.