FindOpenSSL: Report crypto and ssl libraries separately

Some applications only need the OpenSSL crypto library and want to avoid
linking against the SSL library.  Set OPENSSL_CRYPTO_LIBRARY and
OPENSSL_SSL_LIBRARY in the code paths that do not need to find them
separately, and document them publicly.  This allows applications to be
more specific when linking against OpenSSL.
Merge topic 'FindOpenSSL-separate-libs' into next

be9bec5d FindOpenSSL: Report crypto and ssl libraries separately