Including windows.h

[Walter Bright]

Every operating system vendor suffers from the disease of feeling compelled to 
add all kinds of ding-dong extensions to their C compiler, all different from 
every other operating system, and weld them into their ding-dong system .h files.

(The correct way to do this is to make the .h files use Standard C, and relegate 
the ding-dongs to the implementation files that nobody ever needs to see.)

With D, this has resulted in a lot of ugly hacks and workarounds for the 
ding-dong constructions. You can see these in druntime/src/__importc_builtins.di 
and druntime/src/importc.h.

They can help in showing how to deal with windows.h.

An alternative you can try is windows.d in druntime.

If you're blocked, the thing to do is file an issue for each item, and then the 
D community can help out.