unpack-trees: get rid of *indpos parameter.

This variable keeps track of which entry in the original index
the traversal is looking at, and belongs to the unpack_trees_options
structure along with other traversal status information.

Signed-off-by: Junio C Hamano <junkio@cox.net>

unpack-trees.h

@@ -16,6 +16,7 @@ struct unpack_trees_options {
 	int verbose_update;
 	int aggressive;
 	const char *prefix;
+	int pos;
 	struct dir_struct *dir;
 	merge_fn_t fn;