Changes since 1.73:
Version 1.81, 2/5/03
* fflush() wasn't being called after print_results() in xboard().
* hply was being set to 0 when xboard() received "black." This broke the
opening book code when playing black with WinBoard.
* set_hash() wasn't being called in bench().
Version 1.8, 1/30/03
* Added opening book code (book.c) and a small opening book (book.txt).
* Added hash keys; replaced the old repetition detection code with code that
compares hash keys.
* Changed bench to report a "Score" to avoid confusion/comparisons with the
previous version's "MIPS" (with score, 1.000 = my Athlon XP 2000+).
* Moved move parsing into its own function (parse_move in main.c).
