valuehash fails to meet contract for map entries

[cch1]

Consider this expression:

(let [v [:a 1]
      me (find {:a 1} :a)]
  [(= v me) ; true
   (= (valuehash.api/sha-1 v) ; false
      (valuehash.api/sha-1 me))])

=> [true false]

This discrepancy is particularly scary when using disparate mechanisms to construct Datomic lookup refs with the expectation that clojure.core/= (and equivalent Datomic lookup semantics) imply equal hash values.

Observed with ff1d4b7