def meta should be evaluated and support arbitrary values

[frenchy64]

At least if we want Clojure parity, not sure if CLJS does this. clojure.test/deftest uses this.

;jank
clojure.core=> (def ^{:test (fn [])} a)
#'clojure.core/a
clojure.core=> (-> #'a meta :test)
(fn [])

;clj
user=> (def ^{:test (fn [])} a)
#'user/a
user=> (-> #'a meta :test)
#object[user$fn__134 0x4a05d8ae "user$fn__134@4a05d8ae"]

Can't set manually with alter-meta! either:

Exception: invalid meta: clojure.core/clojure_core-fn-4375 (jit_function@0x1117d2008)

[jeaye]

Yep, we should follow Clojure here.