CLJ-1302 - clarify order constraints of keys and vals

Signed-off-by: Stuart Halloway <stu@cognitect.com>
CLJ-1331: Update primitive vectors to use Murmur3 hash

Signed-off-by: Stuart Halloway <stu@cognitect.com>
CLJ-1335: Update hash for empty PersistList and LazySeq

Signed-off-by: Stuart Halloway <stu@cognitect.com>
CLJ-1339 - fix NPE in primitive vector .equals method

Signed-off-by: Stuart Halloway <stu@cognitect.com>
CLJ-1336 - make hashing mixing function available in Clojure for external collections. Add generative tests that check external hashing facilities match internal hashes.

Signed-off-by: Stuart Halloway <stu@cognitect.com>
CLJ-1344 - update mapHasheq function to call Murmur3. This is used by defrecord and some external collections

Signed-off-by: Stuart Halloway <stu@cognitect.com>
CLJ-1345 - update changelog for 1.6

Signed-off-by: Stuart Halloway <stu@cognitect.com>