Rewrite of List.(uniq|squish) using map()

For "my @a=1..100000; my @b= @a.(uniq|squish) the improvements were:
  uniq:   CPU from 0m23.214s to 0m10.107s  (aka 56% less CPU)
  squish: CPU from 0m10.911s to 0m7.790s   (aka 28% less CPU)