Convert lookup_blob to struct object_id

Convert lookup_blob to take a pointer to struct object_id.

The commit was created with manual changes to blob.c and blob.h, plus
the following semantic patch:

@@
expression E1;
@@
- lookup_blob(E1.hash)
+ lookup_blob(&E1)

@@
expression E1;
@@
- lookup_blob(E1->hash)
+ lookup_blob(E1)

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

reachable.c

@@ -88,7 +88,7 @@ static void add_recent_object(const struct object_id *oid,
 		obj = (struct object *)lookup_tree(oid->hash);
 		break;
 	case OBJ_BLOB:
-		obj = (struct object *)lookup_blob(oid->hash);
+		obj = (struct object *)lookup_blob(oid);
 		break;
 	default:
 		die("unknown object type for %s: %s",