Use 'unsigned short' for mode, like diff_filespec does

struct diff_filespec defines mode to be an 'unsigned short'.  Several
other places in the API which we'd like to interact with using a
diff_filespec used a plain unsigned (or unsigned int).  This caused
problems when taking addresses, so switch to unsigned short.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

archive.c

@@ -415,7 +415,7 @@ static void parse_treeish_arg(const char **argv,
 
 	if (prefix) {
 		struct object_id tree_oid;
-		unsigned int mode;
+		unsigned short mode;
 		int err;
 
 		err = get_tree_entry(&tree->object.oid, prefix, &tree_oid,