Stockfish 17042905_Costalba - new version!

Stockfish, chess engine UCI
Leader rating list JCER = 3405
🔬 Author: Marco Costalba


Timestamp: 1493436810 

Retire the misdesigned StepAttacks[] array. 

StepAttacks[] is misdesigned, the color dependance is specific to pawns, and trying to generalise to king and knights, proves neither useful nor convinient in practice. 

So this patch reformats the code with the following changes: 
- Use PieceType instead of Piece in attacks_() functions 
- Use PseudoAttacks for KING and KNIGHT 
- Rename StepAttacks[] into PawnAttacks[] 

Original patch and idea from Alain Savard. 
No functional change. 
Closes #1086 

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