Stop TypeTuple as template parameter from expanding

[Tobias Pankrath]

bearophile wrote:

> "Type tuples" (that are allowed to contain more than just types) aren't
> Phobos constructs, they are built-in in the language.

Haven't tried any of the proposed solutions yet, but they seem all very 
easy.
If the solution were not that simple, std.typetuple could be augmented with
an easy to use one. 

That's what I've tried to say.