Small fix for Self 4.0

[Cameron Elliott]

in the traits slots plain object,
in the 'isArgument: isA IfFail: fb' method,

the following code needs to be changed:

from:

( 
inPlaceIfy: [copyIsArgumentForVisibility: v IfFail: [| :e | fb value: e]
] IfFail: fb
)


to:
( 
inPlaceIfy: [ copyHolderForIsArgument: isA  IfFail: [| :e | fb value: e]
] IfFail: fb
)



Note, isArgument: isn't used in the 4.0 system as distributed,
but hey, might as well fix it, right...

Also, I have conversed with Ole about his type inference code, and 
with someone else about a simplified outliner,
both of which need a post 4.0 sanpshot to work.
I was wondering if there is any plan to make a post 4.0 
release, or if there was any way in which I could contribute
to such an effort.
(I do understand that the Self project has pretty much been
shut down, but at least its worth asking...)


Cameron Elliott