pack_refs() was not using any of the extra features of for_each_ref(),
so change it to use do_for_each_entry(). This also gives it access to
the ref_entry and in particular its peeled field, which will be taken
advantage of in the next commit.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>