openssh: cherry-pick OpenSSL 1.1.1 compatibility

Compatibility with existing OpenSSL versions is maintained.

Upstream commits:
482d23bcac upstream: hold our collective noses and use the openssl-1.1.x
48f54b9d12 adapt -portable to OpenSSL 1.1x API
86e0a9f3d2 upstream: use only openssl-1.1.x API here too
a3fd8074e2 upstream: missed a bit of openssl-1.0.x API in this unittest
cce8cbe0ed Fix openssl-1.1 fallout for --without-openssl.

Trivial conflicts in sshkey.c and test_sshkey.c were resolved.

Connect libressl-api-compat.c to the build, and regenerate config.h

Reviewed by: des
Approved by: re (rgrimes)
MFC after: 2 seeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17444