Add Policy 3.9.6

Signed-off-by: Niels Thykier <niels@thykier.net>
t: Skip "dh_strip_nondeterminism" in a few tests

Signed-off-by: Niels Thykier <niels@thykier.net>
c/testsuite.pm: Recognise autopkgtest-pkg-{perl,ruby}

Signed-off-by: Niels Thykier <niels@thykier.net>