[Dune] Hint: problem in mpihelper

[Bernard Haasdonk]

Hello Duners,

I have different compilation modules, which are based on Dune components 
and I get a "multiple definitions" linkage error of the static member 
variables FakeMPIHelper::instance_ and MPIHelper::instance_
in mpihelper.hh. Indeed these variables are defined explicitly in that 
header file, which makes it only includable in one object file.
I guess it is suggested to be more flexible.

For my local work, putting the whole classes in an 
anonymous namespace works fine as a workaround. However, I do not dare to 
implement a general solution.

Bye,

    Bernard

----------------------------------------------------------------------------
Bernard Haasdonk 
Mathematisches Institut
Abteilung fuer Angewandte Mathematik               Url: www.haasdonk.de
Hermann-Herder-Strasse 10                          Tel: +49-(0)761-203-5639
D-79104 Freiburg i. Br.                            Fax: +49-(0)761-203-5632
----------------------------------------------------------------------------