[Dune-devel] Replace Dune C++11 by plain C++11

[Christian Engwer]

Hi Oli,

I just checked again.

a) with respect to static_Assert I was wrong and we actually decided
   to drop dune_static_assert completely.
b) if we follow you suggestion
   > We cannot drop the namespace imports without deprecating them first.
   > But we can start using the std:: versions explicitly inside the
   > core modules, which is what Christoph did, IIRC.
   we basically revert the decision to have namespace import to ease the
   use of unsupported compilers. Which is something, where I don't have a
   strong opinion, besides we should stick to what we decided until we
   decided differently.

Ciao
Christian