Building Blocks: Add Macro to implement on 0 to n-ary tuples

[Veykril]

One point where macros still shine a lot is when implementing things on a bunch of different tuples to "emulate" variadic generics.

What I mean with this is a macro that when invoked like foo!(A, B, C, D, E) will continue invoking subsets of this, so it will invoked foo!(A, B, C, D)/foo!(B, C, D, E) which then invokes it again for only 3, then 2, then 1 and finally finishes recursing.