penalize pseudo isolated pawns only in endgame (7181778)
tc=inf nodes=40000 book=book.bin
Score of ./chess/test vs ./chess/master: 4731 - 4532 - 5737  [0.507] 15000
roll back chainable pawn stuff (6679687)
The previous bunch of patches, on the idea of chainable pawns, do not scale:
- 10k games at 40k nodes/moves: passed easily with 51.0%
- 10k games in 10"+0.1": regression 49.4%

So roll back, and never cut corners again on the testing. It is possible that the regression is simply due to a slowdown in NPS, or that the patches simply do not scale (even in fixed nodes term).