builtin/blame: convert struct origin to use struct object_id

Convert struct origin to use struct object_id by applying the
following semantic patch and the object_id transforms from contrib,
plus the actual change to the struct:

@@
struct origin E1;
@@
- E1.blob_sha1
+ E1.blob_oid.hash

@@
struct origin *E1;
@@
- E1->blob_sha1
+ E1->blob_oid.hash

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>