[Dune] patch dune-grid r3316

[Christian Engwer]

Dear Carsten,

cou applied patch to test whether copies of entities have the same
global id. To me the grid interface reads such that these id's are
required to be uniq and must be different.

It says if id==id' => entity==entity'. But in case of a copy it is not
the same entity anymore, but only similar.

Therefor I think that your test tests the wrong thing.

Could the others please comment on this issue aswell, perhaps I
misunderstood something.

Christian