[Mondrian] mondrian.rolap.CellKey.Zero

[Anton Nikitin]

It seems that I've found another one bug in ...

Class Zero (inner in mondrian.rolap.CellKey) is intended as singleton, but
actually is not used as singleton. Besides it doesn't override hashCode()
which causes error in some our applications 

(I don't know yet how to reproduce it via original Mondrian -- possibly one
should run MDX which doesn't contain regular axes but maybe contain some
complex calculated members)...

Anton