present in RFC959... so now (lib)curl supports it as well. --ftp-account and
CURLOPT_FTP_ACCOUNT set the account string. (The server may ask for an account
string after PASS have been sent away. The client responds with "ACCT [account
string]".) Added test case 228 and 229 to verify the functionality. Updated
the test FTP server to support ACCT somewhat.