Hello,
I am trying to compile some software that uses `std::optional`, which from
reading a few sites means I need a compiler that supports "C++17" or ISO
C++ 2017 standard. So I installed clang-6.0 on a clean install of
ubuntu/xenial using the packages from llvm.org, but no luck. I am guessing
Well I'll be damned, tried it on Bionic (Ubuntu 18) and it seems to work
just fine:
```
curl -L https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
sudo apt-add-repository "deb http://apt.llvm.org/bionic/
llvm-toolchain-bionic-6.0 main"
sudo apt-get update
sudo apt-get install -y clang
