ZWEI initialization functions

[DOYLE at MIT-AI (Jon Doyle)]

I got annoyed with the habit of ZWEI of starting up with an initial buffer
with package USER and a random directory in the filename.  Thus, my init
file DOYLE;LISPM > contains two functions, SET-INITIAL-FILENAME-DEFAULT,
which takes a filename (e.g. "FOO > DOYLE; AI:") and makes it the initial
default filename, and SET-INITIAL-PACKAGE-DEFAULT, which takes a package
name and makes that the package initially seen in ZWEI.  The latter function
hacks a slot in an obscure ZWEI data structure, so I hope that it can be
made a standard function to avoid lossage in the future if the implementation
of the editor changes.  I wish that LOGIN automatically called the first
function, since it only depends on the user's login name, typically.