Incorrect results with unique of 20 or more elements

[Kacper Gutowski]

Hello,
Unique with argument of 20 or more items gives results 
in an incorrect order:

      ∪'abbbbbbbbbbbaaaaaaa'
ab
      ∪'abbbbbbbbbbbaaaaaaaa'
ba

Or even with wrong set of distinct elements:

      (A B C)←1+¯1 0 1×(⎕CT←1E¯9)÷2
      ∪19↑B A B C
1 0
      ∪20↑B A B C
0.9999999995 1.000000001 0

Looks like the tie breaker used to stabilize the sort 
in src/Cell.cc:130 should be A > B instead of A < B 
if I read it right.

-k