Add dispatch-fn for multimethods

Description

Per https://ask.clojure.org/index.php/10261/please-add-dispatch-fn-to-clojure-core

ClojureScript has `dispatch-fn` method to get the dispatch function for a multimethod. This is available in Clojure as a field on the MultiFn but could improve portability between dialects if Clojure had the same function.

Environment

None

Assignee

Unassigned

Reporter

Alex Miller

Approval

Triaged

Patch

Code

Priority

Major

Affects versions