[dev] function-info command

[shish]

I'm trying to figure out why some functions claim to take a resource when they actually take a FTP\Connection or a GdImage -- this CLI command helps with debugging.

Example:

$ php ./generator/safe.php function-info ftp_alloc
Params:
  ftp
    ParameterType: FTP\Connection
    SignatureType:
    DocBlockType:  resource
  size
    ParameterType: int
    SignatureType: int
    DocBlockType:  int
  response
    ParameterType: string
    SignatureType: ?string
    DocBlockType:  string|null

/**
 * Sends an ALLO command to the remote FTP server to
 * allocate space for a file to be uploaded.
 *
 * @param resource $ftp An FTP\Connection instance.
 * @param int $size The number of bytes to allocate.
 * @param string|null $response A textual representation of the servers response will be returned by
 * reference in response if a variable is provided.
 * @throws FtpException
 *
 */
function ftp_alloc($ftp, int $size, ?string &$response = null): void
{
    error_clear_last();
    $safeResult = \ftp_alloc($ftp, $size, $response);
    if ($safeResult === false) {
        throw FtpException::createFromPhpError();
    }
}

[shish]

(The addition of a seemingly-unused $output parameter is to make this PR compatible with #530)