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>

list-objects.c

@@ -119,7 +119,7 @@ static void process_tree(struct rev_info *revs,
 					cb_data);
 		else
 			process_blob(revs,
-				     lookup_blob(entry.oid->hash),
+				     lookup_blob(entry.oid),
 				     show, base, entry.path,
 				     cb_data);
 	}