ossl.c: OPENSSL_LIBRARY_VERSION

* ext/openssl/ossl.c (Init_openssl): add constant OPENSSL_LIBRARY_VERSION
  which tells the version running OpenSSL.  [EXPERIMENTAL]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45540 b2dd03c8-39d4-4d8f-98ff-823fe69b080e