ImportC can now automatically run the preprocessor

[Walter Bright]

On 5/15/2022 6:16 AM, Vladimir Panteleev wrote:
> I'm looking forward to the future when we can stop worrying and deprecate the 
> entirety of https://github.com/D-Programming-Deimos.

So am I. I'll be happy to bury it.

BTW, if anyone wants to start trying ImportC with Diemos projects, and reporting 
to bugzilla any issues encountered, we can move along even faster!