devel/range-v3 0.12.0p0 OpenBSD

Range library for C++14/17/20. This code was the basis of [a formal proposal](https://ericniebler.github.io/std/wg21/D4128.html) to add range support to the C++ standard library. That proposal evolved through a Technical Specification, and finally into [P0896R4 "The One Ranges Proposal"](https://wg21.link/p0896r4) which was merged into the C++20 working drafts in November 2018.

Ranges are an extension of the Standard Template Library that makes its iterators and algorithms more powerful by making them _composable_. Unlike other range-like solutions which seek to do away with iterators, in range-v3 ranges are an abstration layer _on top_ of iterators.