Inconsistent hash with java collections

c.c/hash always use hashCode for java collections, which is incompatible when comparing with Clojure collections, which use Murmur3.

One way to fix it is to add a special case in Util/hasheq for java.util.Collections, as it is now for Strings.

Link to a discussion of this topic in the Clojure group: https://groups.google.com/forum/#!topic/clojure/dQhdwZsyIEw