Maybe this has been discussed on a meeting without me, so forgive me if this is a repeat. Are we going to commit to use whatever g++ 4.9.3 from RTools provides (full C++11 and some C++14) or are we going to restrict ourselves to C++11?
I am raising this as many clusters nowadays run RHEL7 which brings gcc 4.8.x (x>= 1) with them. That gcc fully supports C++11, but not as much from C++14 as the 4.9.3.
Now there are developer packages available for RHEL which provide even a gcc 6; so it's manageable, but all cluster admins life would be simpler if thing run with 4.8. Just a point to consider.