Adding the ?. null verification

[Etienne via Digitalmars-d]

> This also allows you to do a complete null check in a single statement:
>
> 	if (maybe(tree).left.right.right.left.right !is null) {
> 		// do something with that value
> 	}
>
> If nothing else, this at least saves you the trouble of having to check
> every intermediate reference in the chain. :)
>

Very clever, this should go straight to std.typecons. I'm definitely 
ripping it for my project, if you can just scratch something like a 
boost license on it ;)