LibreSSL 2.7 introduced OpenSSL 1.1.0 API. The ssl module now detects
LibreSSL 2.7 and only provides API shims for OpenSSL < 1.1.0 and
LibreSSL < 2.7.

Documentation updates and fixes for failing tests will be provided in
another patch set.

Signed-off-by: Christian Heimes <christian@python.org>.
(cherry picked from commit 4ca0739c)
Co-authored-by: Christian Heimes <christian@python.org>