Support Chess960

Support Chess960

AIf an engine annunces an option UCI_Chess960 UCI2WB will report to
the GUI it supports variant fischerandom. In addition it will request
the GUI to encode castling moves as KxR through feature oocastle=0.
A flag argument -f will make UCI2WB support FRC even when the engine
does not have the option. In that case the GUI is set to deliver castling
moves as O-O[-O] (feature oocastle=1), and any castling field in a
received FEN will be overwritten with KQkq. (This is the obsolete
'Arena standard' for FRC.)