Compact position structures
Reorder the structures data members in position.h to reduce padding.
Passed STC:
https://tests.stockfishchess.org/tests/view/60a8011fce8ea25a3ef04069
LLR: 2.94 (-2.94,2.94) <-0.50,2.50>
Total: 14120 W: 1214 L: 1067 D: 11839
Ptnml(0-2): 26, 857, 5161, 976, 40
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Also tested for speed locally by Joost:
Result of 50 runs
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base (./stockfish.master ) = 2254919 +/- 4439
test (./stockfish.patch ) = 2274003 +/- 5278
diff = +19084 +/- 6386
==================
speedup = +0.0085
P(speedup > 0) = 1.0000
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closes https://github.com/official-stockfish/Stockfish/pull/3488
No functional change.