Simplify eval take 2.  Bench 5097444

No need to pull this until current master is verified with multiple threads against 2.3.1, but results look really good after nearly 6000 games.  I'll keep running the test overnight.

ELO: 12.09  +- 99%: 11.67 95%: 8.86
LOS: 100.00%
Wins: 1033 Losses: 827 Draws: 4064