- Adds a new modern compressed opening
book with 515k moves for upper difficulty levels, 700x bigger than
old book. This will add much more play diversity and depth. Levels
6->11 also re-graded, and Levels 1 and 2 weakened, in response
to user requests
- Fixes timer bug in 2.51
- 2.512 Fixes very rare bug in new book
look-up