Increase pruning if evaluation is not improving
Add an additional set of margins to movecount pruning
to be used when static evaluation is getting worse
than previous move.
Here are the margins table with changing
depth (fm0 not improving, fm1 improving):
d: 0, fm0: 3, fm1: 3
d: 1, fm0: 4, fm1: 4
d: 2, fm0: 6, fm1: 6
d: 3, fm0: 7, fm1: 10
d: 4, fm0: 11, fm1: 15
d: 5, fm0: 15, fm1: 21
d: 6, fm0: 21, fm1: 29
d: 7, fm0: 27, fm1: 37
d: 8, fm0: 35, fm1: 47
d: 9, fm0: 42, fm1: 57
d: 10, fm0: 51, fm1: 68
d: 11, fm0: 60, fm1: 81
d: 12, fm0: 70, fm1: 94
d: 13, fm0: 81, fm1: 108
d: 14, fm0: 92, fm1: 123
d: 15, fm0: 104, fm1: 139
Good at both short TC
LLR: 2.97 (-2.94,2.94)
Total: 11502 W: 2503 L: 2361 D: 6638
And long TC
LLR: 2.98 (-2.94,2.94)
Total: 7189 W: 1421 L: 1277 D: 4491
bench: 4364793