A reordering / code-split of Telnet in telnetlib.py
into Expect (the lowest base class), TelnetBase, Telnet
and TelnetPopen4.

Reason: Expect contains all of the read_xxx(),
expect(), write() and select() functions (and the
interact() and mt_interact())

TelnetPopen4 and Telnet derive from the same TelnetBase
class, and there is nothing stopping anyone from
writing a TelnetHTTP or TelnetURL class which will all
have the same interface: expect() and write() and even
interact()!

weird, huh - typing in URLs and getting the content
back, interactively :)

these TelnetXXX classes are all incredibly useful for
"remote host management" purposes; also the principle
of the TelnetHTTP class is very useful for doing
automated testing of web sites.  send URL, expect text
in it before proceeding with next URL (e.g. login,
check to see if login failed or succeeded; react
accordingly).