vendoring cpp11 headers

[pachadotdev]

Provided that @Antonov548 migrated all to C++11, it makes sense to use vendoring to count on a more robust codebase.

I will send a PR for this now, where vscode-install.r shows what I did and NEWS.md summarises the change.

[krlmlr]

Thanks for this. Let's continue the discussion in the PR.