Increase weight for supported pawns
This patch changes the weight for counting supports of pawns
from 17 to 21. Hopefully Stockfish will accept to play a bit
more of closed or semi-closed positions.
STC:
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 13822 W: 3158 L: 2939 D: 7725
http://tests.stockfishchess.org/tests/view/5d89c3a10ebc595091802379
LTC:
LLR: 2.96 (-2.94,2.94) [0.00,4.00]
Total: 63066 W: 10590 L: 10236 D: 42240
http://tests.stockfishchess.org/tests/view/5d89ca7f0ebc595091802680
Future work: try to tweak the evaluation to better understand
the French structures.
Closes https://github.com/official-stockfish/Stockfish/pull/2326
Bench: 3618154