fill_stat_cache_info(): prepare for an fsmonitor fix

We will need to pass down the `struct index_state` to
`mark_fsmonitor_valid()` for an upcoming bug fix, and this here function
calls that there function, so we need to extend the signature of
`fill_stat_cache_info()` first.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

apply.c

@@ -4310,7 +4310,7 @@ static int add_index_file(struct apply_state *state,
 						     "created file '%s'"),
 						   path);
 			}
-			fill_stat_cache_info(ce, &st);
+			fill_stat_cache_info(state->repo->index, ce, &st);
 		}
 		if (write_object_file(buf, size, blob_type, &ce->oid) < 0) {
 			discard_cache_entry(ce);