slightly improve maildir rescan debugging

src/drv_maildir.c

@@ -1477,6 +1477,7 @@ maildir_rescan( maildir_store_t *ctx )
 	ctx->fresh[0] = ctx->fresh[1] = 0;
 	if (maildir_scan( ctx, &msglist ) != DRV_OK)
 		return DRV_BOX_BAD;
+	debug( "Maildir processing rescan of %s:\n", ctx->path );
 	for (msgapp = &ctx->msgs, i = 0; (msg = *msgapp) || i < msglist.array.size; ) {
 		if (!msg) {
 #if 0