public key only.
* ext/openssl/ossl_pkey_dh.c (ossl_dh_to_der): new function for
OpenSSL::PKey::DH#to_der.
* ext/openssl/ossl_pkey_dsa.c (ossl_dsa_to_der): new function for
OpenSSL::PKey::DSA#to_der.
* ext/openssl/ossl_pkey_rsa.c (ossl_rsa_to_der): new function for
OpenSSL::PKey::RSA#to_der.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@5417 b2dd03c8-39d4-4d8f-98ff-823fe69b080e