C++17's <memory_resource> header

This is a work in progress implementation of the <memory_resource> header from C++17. I haven't found any standard library implementation that implemented this header up until now, and I needed some of its utilities, so that's my motivation to work on it.

Features implemented so far are:

• Class memory_resource
• Class polymorphic_allocator
• Class synchronized_pool_resource
• Class unsynchronized_pool_resource
• Class monotonic_buffer_resource
• Function new_delete_resource()
• Function null_memory_resource()
• Function set_default_resource()
• Function get_default_resource()

License

Distributed under the Boost Software License, Version 1.0. See LICENSE.