Module closures

[foxfriends]

Would it be too much to make module closures too? Then modules/types/classes really do all become one thing, and it all kind of makes sense...

proc main!() {
  let collector = mod {
    proc empty!() { return [] }
    func append x y = [x]
    func of x = [x]
  }

  iter::collect collector (iter::of [1, 2, 3])
}

Probably decide if type and ty is the better choice than module and mod.