Switch to using OpenSSL target names in CMakeLists.txt

Cmake 3.0 was a switch to using targets and properties rather than
variables when linking different components together.
We follow that philosophy by dropping ${OPENSSL_CRYPTO_LIBRARIES} and
${OPENSSL_SSL_LIBRARIES} in favor of OpenSSL::Crypto and OpenSSL::SSL.

(cherry picked from commit 36c50fa5)

# Conflicts:
#	CMakeLists.txt