Changing default cxx_stdlib to libc++

[db]

On 10 Mar 2018, at 18:06, "Kenneth F. Cunningham" <ken.cunningham.webuse at gmail.com> wrote:
> I think I"m likely not going to change anything on my LibcxxOnOlderSystems 10.6.8 system for a while, db. It will continue to work just as it does now, and I don't mind building from source -- kinda got used to it.

Except for building from source for minor versions and revbumps, especially large binaries, and for ports that have open defects. Oh well…