[mod_python] retaining state between handlers

For those of you handy with CVS - I've checked in the new version, where
the request object is a real Python object (as opposed to a built-in),
which you can modify.

This allows passing information between handlers by simply doing something
like:

req.myvariable = "something"

in one handler and then using that value in another. 

Note that different subinterpreters will have different requests objects,
even though the underlying built-in (now req._req) is still the same.

--
  Gregory (Grisha) Trubetskoy
       grisha at modpython.org