       you use -DDIRENT).
# -DNO_MEMORY_H         If USG or STDC_HEADERS but do not
#                       include memory.h.
# -DDIRENT              If USG and you have dirent.h
#                       instead of ndir.h.
# -DSIGTYPE=int         If your signal handlers
#                       return int, not void.
# -DNO_MTIO             If you lack sys/mtio.h
#                       (magtape ioctls).
# -DNO_REMOTE           If you do not have a remote shell
#                       or rexec.
# -DUSE_REXEC  