Conditional compilation

[Chris Nicholson-Sauls]

There is the aforementioned extern(system), which is probably 
your best bet.  But I'm wondering if your design could seperate 
the connection to IUnknown for non-Windows builds?  Something 
like this:

version(Windows) interface _Inter_ : IUnknown {}
else interface _Inter_ {}

// later

interface InterfaceA : _Inter_ {
     //...
}