test suite: Introduce t-ok.

test suite: Introduce t-ok.

No functional change.

 perl -i~ -pe 's/^echo ok\.$/t-ok/' tests/tests/*[^~]
 perl -i~ -pe 's/^echo ok\.$/t-ok/' tests/setup/*[^~]
 perl -i~ -pe 's/^echo done\.$/t-ok/' tests/tests/*[^~]
 perl -i~ -pe 's/^echo done\.$/t-ok/' tests/setup/*[^~]

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>