2.7.23 released January 26, 2000

- removed inclusion of unistd.h where unnecessary
- include io.h on platforms where unistd.h not available
- remove unused files utils/long-options.[ch] utils/closeout.[ch], and
  utils/error.h 
- fixed getopt warnings by renaming the getopt in utils/ to gg-getopt
- TODO revised
- -M option repaired
- bugfix in init_gnugo() in board.c; don't do everything twice
- default size of reading cache increased from 8 MB to 32 MB
- docs/ directory replaced by doc/ with texinfo documentation from 2.5.60
- gnugo.6 man page moved from top directory to doc/
- /docs/WINDOWS updated from 2.5.60 and moved to top directory