Thoughts on std.system.OS

[Jonathan M Davis]

I made a few changes to std.system to clean it up a bit and make it more 
thorough:

https://github.com/D-Programming-Language/phobos/pull/186

However, on reflection, I'm not convinced that the OS enum and its 
corresponding os variable along with the os_major and os_minor variables serve 
any real purpose. Their purpose appears to be to tell you at runtime which OS 
you're actually running on - as in version, not just family of OS. I don't see 
how this is actually possible outside of perhaps Windows (it's just defaulted 
to WindowsXP thus far). And if it can't really do its job, I'd just as soon 
remove it. And since it hasn't been in the documentation, it's not likely to 
break any code.

Thoughts on std.system.OS? Is there a good reason to leave it? In principle, 
it's a nice idea, but I just don't see how it can deliver. And if it can't 
deliver, it should be removed IMHO. What do you think?

- Jonathan M Davis