[Feature Request] Undeclared traits

[jecisc]

We have a Undeclared classes mechanism en Pharo when we are subclassing a non existing class for example and it is really nice.

But we have nothing on the sort when we are referencing a non existing trait in a trait composition. It would be nice to have an equivalent system. This would solve a lot of problems while loading code for example if we have dependencies troubles.

[Ducasse]

:) First we should get UndefinedClass working but yes this is a good idea.