Drop 'Set to' from most src.conf(5) knobs

The description is clearly what effect the knob has when set, so the
additional text was unnecessary.

Reviewed by: jhb, se
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D29583

OpenSSL: Support for kernel TLS offload (KTLS)

This merges upstream patches from OpenSSL's master branch to add
KTLS infrastructure for TLS 1.0-1.3 including both RX and TX
offload and SSL_sendfile support on both Linux and FreeBSD.

Note that TLS 1.3 only supports TX offload.

A new WITH/WITHOUT_OPENSSL_KTLS determines if OpenSSL is built with
KTLS support. It defaults to enabled on amd64 and disabled on all
other architectures.

Reviewed by: jkim (earlier version)
Approved by: secteam
Obtained from: OpenSSL (patches from master)
MFC after: 1 week
Relnotes: yes
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D28273