Create a new instance of a class without indexed instance variables.
The instance is guaranteed not to move across garbage collections.
If a subclass overrides #new, the changes will apply to this method too.
newInFixedSpace: numInstanceVariables
Create a new instance of a class with indexed instance variables. The
instance has numInstanceVariables indexed instance variables. The
instance is guaranteed not to move across garbage collections. If
a subclass overrides #new:, the changes will apply to this method too.