def-map-type breaks in namespaces that shadow core Clojure methods like instance?

[camsaul]

If you have a namespace that does something like :refer-clojure :exclude [instance?] and use def-map-type in it,

(merge instance-of-my-map-type nil)

will break because

def-map-type uses the def-abstract-type AbstractMap which defines cons like this:

potemkin/src/potemkin/collections.clj

Lines 68 to 79 in f22d972

	(cons [this o]
	(cond
	(map? o)
	(reduce #(apply assoc %1 %2) this o)
	(instance? java.util.Map o)
	(reduce #(apply assoc %1 %2) this (into {} o))
	:else
	(if-let [[k v] (seq o)]
	(assoc this k v)
	this)))

and the ultimate macroexpansion copies that call to instance? directly, rather than qualifying it as clojure.core/instance?.