Update HashSet.scala

revert sudden change
make collections shuffle stable.
Merge branch 'new-hashset-impl' of https://github.com/SoftageRnD/scala into new-hashset-impl
Caliper benchmarks update. Count objects was changed to 1000000. Random generator was made constant.
undo wrong update
Merge remote-tracking branch 'origin/new-hashset-impl' into mci/revert-eq-null

Conflicts:
	src/library/scala/collection/mutable/experimental/HashSet.scala