gnuchess2 on the 3b1 problem

[Dr. Arthur Wouk]

i have been trying to compile gnuchess2 on a 3b1 running release 3.51.

i have attempted both cc and gcc with the same result:
  
  	cat gnuchess.c1 gnuchess.c2 >gnuchess.c
  	touch src-catted
  	gcc -O -c gnuchess.c
  	gcc -O -c uxdsp.c
  uxdsp.c: In function SaveGame:
  uxdsp.c:689: `W_OK' undeclared (first use this function)
  uxdsp.c:689: (Each undeclared identifier is reported only once
  uxdsp.c:689: for each function it appears in.)
  *** Error code 1

what is the signal W_OK which is used in the SaveGame subroutine?
i would like to find some way around it to permit compilation of a
chess game with a book and some intellectual capabilities for the
3b1.