Add a plain performance test for "fsck". This test will not be used to
/ referred to in any upcoming commit of mine in this series, but
having a simple test for fsck performance is valuable, so let's add it
while we're at it.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
