Add ImportC compiler to dmd

[Walter Bright]

On 5/9/2021 2:50 PM, bachmeier wrote:
> This will be incredible. I have a lot of use cases for it. In particular on 
> Windows where linking to DLLs is not fun.

It never occurred to me that this might be a solution to that problem (rather 
than adding a bunch of wacky extensions to D).

This kind of unexpected benefit is exactly why I'm doing this!