Epetra requires C++11 now; update documentation

Created by: mhoemmen

I merged the following pull request that fixes GLIBCXX debug checking for deal.II's tests:

https://github.com/trilinos/Trilinos/pull/2783

This pull request introduces a modest C++11 requirement into Epetra. Please see discussion there for rationale. In particular, no one could come up with a current use case demanding that Epetra be built with a C++98 compiler. Even the Epetra-only MueLu build for Windows requires Teuchos, which in turn requires C++11. More importantly, we have no idea if Epetra builds with a C++98 compiler, since we have not tested this use case for a long time.

@trilinos/epetra @trilinos/framework @trilinos/muelu @maherou @trilinos/tpetra

If y'all have a problem with that, now might be a good time to say something. Otherwise, I hereby declare that Epetra now requires C++11. Next step is to update Epetra's documentation to make this clear.