restore ssl functionality with openssl

The "libressl compatibility" unfortunately added a dependency on the
SSL_CTX_set1_groups() function, which is neither available in base (for
released versions of FreeBSD) nor ports openssl (it's only in openssl-devel
and libressl). This broke SSL (most importantly HTTPS) functionalty
in many Qt5-ports.

This adds some #ifdefs around the SSL_CTX_set1_groups() calling sites
and restores the old code in cases where libressl has not been detected.

PR: 218421
Reported by: yuri
Approved by: maintainer-timeout