Simplify Away Quadruple Extensions
Passed Non-regression LTC:
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 95856 W: 24551 L: 24404 D: 46901
Ptnml(0-2): 85, 10621, 26364, 10778, 80
https://tests.stockfishchess.org/tests/view/679a9aedae346be6da0eebd6
Passed Non-regression VLTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 157536 W: 40000 L: 39921 D: 77615
Ptnml(0-2): 43, 16416, 45775, 16487, 47
https://tests.stockfishchess.org/tests/view/679aed8f51037ccaf3e30fbf
Passed Non-regression VVLTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 51598 W: 13345 L: 13172 D: 25081
Ptnml(0-2): 0, 4735, 16162, 4896, 6
https://tests.stockfishchess.org/tests/view/679d368b0774dfd78deb0163
closes https://github.com/official-stockfish/Stockfish/pull/5843
Bench: 2399312