Stockfish 2.1.1

This is a maintenance release to fix the book reading issue reported by some users. As an added benefit, Jim’s build should be now a little faster on Intel CPU (4% on 64-bit and almost 6% on 32-bit).

This is a non functional change release so there is no need to retest Stockfish for people who have already done so; for people who still to test we suggest to use this one because it should be a bit faster on Intel hardware.