Raising the minimum required LLVM version to 3.9

[Jacob Carlborg]

On 2018-10-08 21:02, Johan wrote:
> Hi all,
>    Martin opened a PR that removes support for LLVM below 3.9.
> https://github.com/ldc-developers/ldc/pull/2872
> 
> I'm in favor of it. LLVM 3.9 is 2 years old, and it's a burden to 
> support so many LLVM versions.
> 
> Are there any good reasons to keep supporting LLVM < 3.9?

Please go ahead.

-- 
/Jacob Carlborg