This should be #include <__tuple>
This line should be gone.
Clean some minor cruft from src/experimental/memory_resource.cpp. (This part is a separate git commit which I could pull-request if you want it separately.)
I wonder if memory_resource needs a key function for its vtable; consider the precedent of D27387. But out-of-lining a trivial destructor just to avoid -Wweak-vtables feels kind of awful.
Experimental and std differ in their implementation of options() because the latter needs to be compileable as -std=c++11 whereas the former gets to use -std=c++14.