Use ALL_PIECES value to reference attackedBy

No functional change
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' into passed_pawns
Passed pawn evaluation change

From the position referenced in Gary's KNPKB endgame change it appears
to me that we overvalue passed pawns that can't promote due to
attackers.

This version appears to hold it's strength (approx +7 ELO) in tests at
5s, 15s and 60s in 1000 game tests.
Currently testing at 60s+0.05 with 4GB hash tables