- SSLContext#client_cert_cb is a Proc. it is called when a client
    certificate is requested by a server and no certificate was yet
    set for the SSLContext. it must return an Array which includes
    OpenSSL::X509::Certificate and OpenSSL::PKey::RSA/DSA objects.
  - SSLContext#tmp_dh_callback is called in key exchange with DH
    algorithm. it must return an OpenSSL::PKey::DH object.

* ext/openssl/ossl_ssl.c:
  (ossl_sslctx_set_ciphers): ignore the argument if it's nil.
  (ossl_start_ssl, ossl_ssl_write): call rb_sys_fail if errno isn't 0.
  [ruby-dev:25831]

* ext/openssl/ossl_pkey.c
  (GetPrivPKeyPtr, ossl_pkey_sign): should call rb_funcall first.
  (DupPrivPKeyPtr): new function.

* ext/openssl/ossl_pkey_dh.c: add default DH parameters.

* ext/openssl/ossl_pkey.h: ditto.

* ext/openssl/lib/openssl/cipher.rb: fix typo. [ruby-dev:24285]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@8129 b2dd03c8-39d4-4d8f-98ff-823fe69b080e