[boost] Adding polymorphic_value to boost

Subject: [boost] Adding polymorphic_value to boost
From: Jonathan Coe (jonathanbcoe_at_[hidden])
Date: 2017-11-16 09:14:30

I'd like to propose adding the class-template `polymorphic_value` to boost.

`polymorphic_value` is designed to allow the compiler to correctly generate
special member functions for classes with polymorphic components (It's
`any` with an interface).

`polymorphic_value` has been proposed for standardisation in P0201 and has
advanced through the Library Evolution group in Albuquerque (Nov 5-10).
https://wg21.link/p0201

A working draft of the proposal and implementation can be found at
https://github.com/jbcoe/polymorphic_value

I gave a presentation about polymorphic_value at C++::London here:
https://skillsmatter.com/skillscasts/9539-a-polymorphic-value-type-for-c-plus-plus

Matt Calabrese has kindly offered to be review manager.

Kind regards,

Jon