Fix up TK library usage for Python 3

* “Tkinter.tkinter” in Python 2 provided IO event handling; in Python 3 it
  looks like this has to be called on a Tk() or widget object

Inspired using “2to3”.
Other module name changes only made in Python 3, inspired using “2to3”

* builtins, html.entities
* Python 3 doesn’t have reload() in the built-in namespace
Update HTTP subclass with HTTPConnection subclass for Python 3
Use “email” module over “rfc822” and “mimetools” modules

* The modules were deprecated in Python 2.3 and removed in 3
* Parse HTTP header at the time its end is known in pollmeta()
Fix up protocol getdata() APIs to return bytes

If the data ends up being decoded to text again (e.g. text/* content types),
some of this will be redundant
Force HTTP 1.0 like the pre Python 3 version used