tree a822b947267f2f4661eb6ad0f8e0237481f427f5
parent 523de29803a3c273e75d2705502b2cbd4f8b1f27
author Mike Vitus <vitus@google.com> 1517003486 -0800
committer Mike Vitus <vitus@google.com> 1519256406 -0800

Adds a ThreadPool and a thread-safe ConcurrentQueue.

This is in preparation for adding support for a C++11 based parallel
for implementation. The code is behind CERES_USE_CXX11_THREADS which
is not exposed to the user yet.

Tested by building with and without CERES_USE_CXX11_THREADS defined
and the tests pass.

Change-Id: I60f5730fa055feeb0ee0fa6c980633aebd8d87b4