expand_pair

# File ext/openssl/lib/openssl/x509-internal.rb, line 81
        def expand_pair(str)
          return nil unless str
          return str.gsub(Pair){
            pair = $&
            case pair.size
            when 2 then pair[1,1]
            when 3 then Integer("0x#{pair[1,2]}").chr
            else raise OpenSSL::X509::NameError, "invalid pair: #{str}"
            end
          }
        end