Merge pull request #2063 from tinwelint/2.1-merge-2.0

2.1 merge 2.0
Primitive long hash set that uses hop-scotch hashing

Hop-scotch hashing is an algorithm for dealing with conflicts coming from
hashing values to an index and not really about the hashing itself, as any
hash function can be used with it.

Measured to be faster, for both putting and getting, than trove4j and
substantially less, also dry code. The algorithm itself is pulled out into its own
class and clocks in on about 200-300 LOC, whereas the hash set/map
implementations merely calls that algorithm by using one-liner method
implementations. The state itself is abstracted into a Table interface
which is trivial to implement with, for example a primitive long[], a
combination of long[] and int[] for a long->int primitive map, a.s.o.

Implementation was driven by an iterative randomizing testing framework
also added in this commit where actions are defined, for example "add" and
"remove" with checks that goes with the actions. In the event a check not
returning OK the execution stops, reduces the list of actions down to a
minimum (by brute-force-reduction one action at a time) and finally prints
a java-code test case to reproduce the problem. Confidence in the code is
very high since it has been tested for a very large combination of values
and sizes.

We should use these primitive sets/maps everywhere we've got a
single-threaded use case and the key is an int or long.