This fixes a long-standing bug on FreeBSD using http but not https. Files were getting truncated at 1MB. This was due to improper usage of sendfile(2), and not testing the http path since I only use mini_httpd for https. Since Linux has a completely different sendfile(2) call, it was not affected. And since https does not use sendfile(2), it also was not affected.
New tarfile available on the mini_http web page.