This is a breaking change that changes the signature, sorry -- if you
were using concatenate() for mesh concatenation before, enjoy the new
less strange signature, if you were using it for making the mesh owned
before (which was a strange and not very well thought out use case),
please use the recently added owned() instead. I thought about adding an
overload for backwards compatibility, but it would need to allocate to
work. This way with the breakage it's ensured you actually change to the
right API.
This also cleans up a lot of ugly code in the internals and resolves one
XFAIL in removeDuplicates().
Vladimír Vondruš