[phobos] std.datetime fails on OSX

[Walter Bright]

Jonathan M Davis wrote:
> I'll make the leap-seconds test Linux-only when I do a check-in later this 
> evening, unless you need it right away, at which point I can do it now (it's 
> just that that's a bit more of a pain for me, since I'm in the middle of some 
> other changes and svn's branching capabilities suck).
>
>   

Thanks. Please fix the path thing, too. Also, would it be better instead 
of versioning the code, to test to see if the 'right' directory exists, 
and make a decision on that?