I've got a throwing destructor. It was by design in the 1990s, but its
showing its age now. We can't yank it because we can't perform the
major version bump at the moment.
I'm trying to abstract noexpct away for the various compilers.
Microsoft added it at VS2015. GCC added it at 4.6. But I'm not sure
when Clang added it (does this page indicate it was 3.0:
When did Clang/LLVM add noexcept?
Thanks in advance.