This is a complete but partly silly implementation of C++17 <memory_resource>.
Potential issues with this patch:
- monotonic_buffer_resource is complete and IMHO well tested, but I bet someone can find suboptimal things in its design.
- unsynchronized_pool_resource is trivial; it ignores the pool_options and just passes everything through to the upstream, which is conforming but I'm sure someone has a better idea.
- unsynchronized_pool_resource is "code complete" but untested.
I feel guilty about (3) and will fix it eventually. I'm willing to take a stab at (2) if anyone can explain in English what the _intended_ implementation is. On (1) I hope there will be only easy nits.