Merge from nginx-devel:

Add kernel TLS option.

It's possible to build nginx on FreeBSD13 with security/openssl port, compiled with kernel TLS option as well.

Based on: https://github.com/nginx/nginx/compare/branches/stable-1.16...bsdjhb:ktls-1.16
Reviewed by: jhb
Tested by: jhb

Sponsored by: Netzkommune GmbH