Run code quality scripts through TAP::Harness instead of 'prove'.

Calling 'prove' to run code quality tests makes it too easy to
overlook results when subsequent outputs follow. With TAP::Harness all
tests become part of the same test summary at the bottom (less
scrolling).

Internal harness tests will be added shortly.

The output may be slightly different compared to 'prove'.

Signed-off-by: Chris Lamb <lamby@debian.org>