SKIP messages are now part of the TAP plan. A TAP harness now knows
why a particular test was skipped and can report that information. The
non-TAP harness built into Git's test-lib did nothing special with
these messages, and is unaffected by these changes.
Signed-off-by: NÆvar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>