Remove pawn count in space() calculation #2139

Remove pawn count in space() calculation #2139

Simplification. Various attempts to optimise the pawn
count bonus showed little effect, so remove pawn count
altogether and compensate by subtracting 1 instead of 4.

STC 10+0.1 th 1:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 152244 W: 33709 L: 33847 D: 84688
http://tests.stockfishchess.org/tests/view/5cceed330ebc5925cf04170e

LTC 60+0.6 th 1:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 24100 W: 4079 L: 3964 D: 16057
http://tests.stockfishchess.org/tests/view/5cd5b6b80ebc5925cf04e889

Bench: 3648841