Python: Be portable by using our own library

Added pystdlib.zip, which contains the bare necessities to get Python to
start up on its' own, and have Python search there for standard library
utilities. This will enable PyGZDoom to be portable without requiring a
system installation.

Currently there are no standard in/out streams, so Python complains
about that at the moment, but next up on the list is to fix that by
adding a module to interact with the ZDoom console.