support for typing annotations

[obriencj]

augment the function and define specials to support optional typing hints

potential examples

(define [foo :type int] 100)
(def function [do-something :type int]
   [[a type: str] [b type: int] [c: "Hello" type: str]]
   ... )

potentially this could augment the existing binding spec as well

(let [[foo as: inner-foo type: int]
     [(do-something 9) as: bar type: Any]
     [food 'tacos type: symbol]]
   ...)

[obriencj]

As a side-effect, the augmented function syntax might also be the right way to do decorators.