Def propagation

[arrdem]

Consider

(def foo (fn [x] x))
(def bar foo)

Uses of bar can trivially be rewritten to be uses of foo, and this would allow for the elimination of bar as a definition entirely in favor of foo. This is a special case of constant folding, but a valuable one as it allows for the elimination of var aliases and subsequently permits inlining, static arity resolution and other tricks.

[arrdem]

Closed as this is a goal of #10