c/driver: evaluate C++ backports library

[lidavidm]

We're stuck on C++11 due to certain R distributions; we could at least get some standard library features through backports, though, e.g. https://github.com/bitwizeshift/BackportCpp

[lidavidm]

What might be useful are

• make_unique
• string_view (to deal with Arrow strings)
• span (to deal with Arrow bytestrings)
• expected (to deal with return values in internal implementations)
• fmt (since we do a lot of string building)

[WillAyd]

Worth closing now that we are on C++17?

[lidavidm]

fmt, expected may still be useful but I think #1663 means we won't want to use expected and fmt is already there. span may be useful but isn't a big deal. So ok, let's close this.