Variadic templates

[Walter Bright]

See http://www.digitalmars.com/d/variadic-function-templates.html

Why now? Because it's such a pain to do template programming without 
them, and because I wanted to have a good signals and slots 
implementation. That was the last piece needed to make S&S work right 
(unless I'm way off track with it).

There's a lot of unexplored territory with the tuples, they should be 
able to do a lot more than the current rather limited ability.