Convert the declaration of struct sha1_stat. Adjust all usages of this
struct and replace hash{clr,cmp,cpy} with oid{clr,cmp,cpy} wherever
possible. Rename it to struct oid_stat.
Rename static function load_sha1_stat to load_oid_stat.
Remove macro EMPTY_BLOB_SHA1_BIN, as it's no longer used.
Signed-off-by: Patryk Obara <patryk.obara@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>