These D versions should also be reserved:

PPC
	PowerPC 32-bit architecture

PPC64
	PowerPC 64-bit architecture


darwin
	Darwin-based OS, including Mac OS X

There isn't really a way to tell between
Darwin and Mac OS X, but one could add a
D version for the "MacOSX" subset of it...


There probably should be an official version
for BSD (e.g. FreeBSD), but I'm not sure what?
Cygwin is another possible platform to consider.

--anders