Igel 3.8.0

What's new:

• implement null move pruning verification search
• store probcut result in tt
• support systems with small stack size (such as alpine linux)
• tune 42 search parameters with spsa (400k games)
• implement capture history
• cache accumulator
• implement adaptive lmr
• implement correction history
• release new standard network 6b953e78
• store static evaluation in tt
• fix insufficient material detection
• handle en passant in tb root probing
• update statistics for tb moves

Regression run against Igel 3.7.0 at Long Time Control (60+0.6)

Elo   | 65.28 +- 4.41 (95%)
Conf  | 60.0+0.60s Threads=1 Hash=64MB
Games | N: 5600 W: 1908 L: 868 D: 2824
Penta | [5, 255, 1249, 1277, 14]
https://chess.grantnet.us/test/40975/

Regression run against Igel 3.7.0 at Short Time Control (10+0.1)

Elo   | 62.51 +- 3.58 (95%)
Conf  | 10.0+0.10s Threads=1 Hash=8MB
Games | N: 10000 W: 3414 L: 1634 D: 4952
Penta | [22, 547, 2163, 2165, 103]
https://chess.grantnet.us/test/40970/