Fix endgame evaluation for large-board version

Fix endgame evaluation for large-board version

Map squares to 8x8 board to retain endgame evaluation logic.
Allows to enable endgame evaluation for large-board variants.

capablanca STC
LLR: 2.99 (-2.94,2.94) [-10.00,5.00]
Total: 2512 W: 980 L: 941 D: 591
http://www.variantfishtest.org:6543/tests/view/5dea40ff6e23db1ffe4a289c

capablanca LTC
LLR: 2.98 (-2.94,2.94) [-10.00,5.00]
Total: 1443 W: 534 L: 490 D: 419
http://www.variantfishtest.org:6543/tests/view/5dea8b666e23db1ffe4a28a6

makruk STC
LLR: 3.00 (-2.94,2.94) [-10.00,5.00]
Total: 1810 W: 158 L: 124 D: 1528
http://www.variantfishtest.org:6543/tests/view/5dea3f546e23db1ffe4a289a

makruk LTC
LLR: 3.01 (-2.94,2.94) [-10.00,5.00]
Total: 795 W: 77 L: 41 D: 677
http://www.variantfishtest.org:6543/tests/view/5dea8b7a6e23db1ffe4a28a8

chess STC
LLR: 2.99 (-2.94,2.94) [-10.00,5.00]
Total: 4321 W: 959 L: 936 D: 2426
http://www.variantfishtest.org:6543/tests/view/5dea398f6e23db1ffe4a2896

chess LTC
LLR: 2.96 (-2.94,2.94) [-10.00,5.00]
Total: 3451 W: 667 L: 640 D: 2144
http://www.variantfishtest.org:6543/tests/view/5dea633a6e23db1ffe4a28a4