* ext/openssl/ossl_x509attr.c (ossl_x509attr_set_value): check that the
argument is an OpenSSL::ASN1::Data before converting to ASN1_TYPE.
This fixes SEGV on OpenSSL::X509::Attribute#value=(non-asn1-value).
* test/openssl/test_x509attr.rb: add tests for OpenSSL::X509::Attribute.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55071 b2dd03c8-39d4-4d8f-98ff-823fe69b080e