Increase non-PV IID search depth

bench: 5146380
Merge branch 'master' into increase_iid
Set IID half way between d/2 and d-4

Master IID formula is depth / 2
Previous patch is depth - 4 * ONE_PLY

This one is the middle way:

(dept/2 + depth-4*ONE_PLY)/2  -> depth-2*ONE_PLY-depth/4

After 16000 games at 60+0.05 th 1
ELO: 4.08 +-3.1 (95%) LOS: 99.5%
Total: 16000 W: 2742 L: 2554 D: 10704

bench: 4781239
Revert "patch1 (5042467)"

Failed in testing (15+0.05)

ELO: -6.88 +-4.3 (95%) LOS: 0.1%
Total: 10057 W: 1909 L: 2108 D: 6040

This reverts commit 172f5568159e29fedd97527a24fe34695e767e8c.
remove pvnode conditions only (4092610)
Merge branch 'master' into lucas_qsearch_pruning

bench 4442332