C++ Container equivalents

[Christian Kamm]

> Arclib has a RedBlackTree class, and I made some changes to that for my
> own purposes. It implements set and multiset.
> http://www.billbaxter.com/projects/d/redblacktree.d

I like those changes, so I took the liberty of changing ArcLib's copy to
your version, modified for tango.
http://www.dsource.org/projects/arclib/browser/trunk/arc/templates/redblacktree.d

Cheers,
Christian