Tpetra: Fix #4729

Created by: mhoemmen

@trilinos/tpetra

Description

• Remove use of C++11 thread stuff from Tpetra::Details::Behavior.
• Fix Tpetra build warnings observed on the Dashboard

Motivation and Context

1. GCC annoyingly requires linking with libpthread in order for that stuff to work. GCC apparently generates code that crashes, if Trilinos was not built with libpthread support. I consider that a GCC bug, but we have to work around.
2. std::call_once etc. only help with thread safety of code that uses std::thread threads. They don't help with other thread models, like OpenMP (or even Pthreads). This reduces the value of this feature.

Related Issues

• Closes #4729 (closed)