for-each-ref: document `creatordate` and `creator` fields
for-each-ref: document `creatordate` and `creator` fields

These were introduced back in 2006 at 3175aa1ec28c but
never documented.

Signed-off-by: Eric Wong <8c2951295f8292b0c03727bc4652981172298eae@yhbt.net>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git