todo

在ftplib-3.1-1-linux.tar.gz,修改了一个BUG,和增加了一个函数

Here are some things which users have asked for that I haven't gotten
around to yet or haven't figured out how to implement yet.

- Percentage complete indication - DONE V3.1

	Do I want to do this in ftplib.c or somehow tie it into allowing
	the user program to do the I/O?  I could parse the size out of
	the 'retr' response and give it to the user.  Let the user do the
	calculations while they are reading/writing the socket.

- C++ support

	I haven't done enough C++ to be able to generate the object model
	myself.  I'm open to ideas on how to set this up.

- Thread safe

	I've been informed that gethostbyname() and getservbyname() are
	not re-entrant although I don't know how to get around them.

- Callback Support - DONE V3.1

	Allow specification of a routine to be called while waiting on
	the network.  This might be useable to update a progress
	indicator or handle events in a windows program.