Wrapper notation specs

Idea: `myfunc :: othermodule:similarfunc/2` ie. use `-spec`s from other modules (DRY). (Makes sense together with wrapper-notation) Enable only for STDlib? (because loss of modularity)

```haskell
zip :: lists:zip/2
# <=> zip :: ([<term>], [<term>]) -> [{<term>,<term>}]
zip ([X|Xs], [Y|Ys]) =
    [{X,Y} | :(Xs, Ys)]
zip ([], []) = []
```