Allow partial matching of keys not existing in a map

Description

When matching maps, it is sometimes useful to specify a map that doesn't include specific keys.

Eg. to specify a map that doesn't include a :foo key:

(def _! :clojure.core.logic/not-found)
(run* [x]
  (featurec x {:foo _!}))

The patch is minimal, and demonstrates the functionality.

None

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Created May 20, 2015 at 6:21 PM

Updated May 20, 2015 at 6:21 PM