Folks -

Since I just integrated Igor's Set with nil support into our production 
images (after finding a heinous method called setSize in class Bag which 
people used to write aCollection asBag setSize instead of aCollection 
asSet size) I did the same in the trunk.

I found that the code was already rotten a bit but hopefully the tests 
account for most of it. Test coverage is probably incomplete in 
particular for cases involving nil; more tests are definitely helpful. 
And of course if you find any issues with the changes please report them.

Cheers,
   - Andreas