Topic/thread framework
Created by: hppritcha
Add a framework to support different types of threading models including user space thread packages such as Qthreads and argobots:
https://github.com/pmodels/argobots
https://github.com/Qthreads/qthreads
The default threading model is pthreads. Alternate thread models are specificed at configure time using the --with-threads=X option.
The framework is static. The theading model to use is selected at Open MPI configure/build time.