[Therion] metapost: Therion version and current date

[Bruce]

>In fact TeX has its own \day, \month and \year (all numeric). You can
>find an example of converting month number to name at
>http://www.alfredklomp.com/programming/tex/macros/ (section 2)

Thanks, that works nicely now.
I'll put an example on the wiki when once we get a \thversion implemented...

I'm having some challenges with adding it to tex-atlas, but I'll work on it
some more before bothering y'all.

Bruce