Multiple-OS Header Access

[Malkierian]

Alright, so I'm making a little utility, and it looks like I'm 
going to need to access OS-specific header functions on each 
operating system in order to make it work, because 1) I want to 
get a list of all active processes and their names and 2) I want 
to periodically check which window currently has focus.  I've 
already found SetWinEventHook and GetForegroundWindow (for 
checking the foreground window and setting an event hook for 
focus change), and also EnumProcesses for getting the list, but 
these are all Windows specific, not to mention C++ specific on 
Windows, and I can't see any way of making one set of functions 
that would work on Windows, Mac and Linux.

So anyway, my question is, does D have the capability of 
interfacing with Linux and Mac such that those functions are 
accessible, and/or would I be better of working in C++ for this 
particular venture?  How would I go about accessing those 
functions, and using the information they provide in D?