Re-add definition for R_OK. Can we think of any OS which might not have unistd.h to supply this definition?
Re-add definition for R_OK. Can we think of any OS which might
not have unistd.h to supply this definition?

ellson/graphviz,jho1965us/graphviz,pixelglow/graphviz,pixelglow/graphviz,jho1965us/graphviz,BMJHayward/graphviz,jho1965us/graphviz,MjAbuz/graphviz,MjAbuz/graphviz,BMJHayward/graphviz,kbrock/graphviz,pixelglow/graphviz,tkelman/graphviz,kbrock/graphviz,MjAbuz/graphviz,kbrock/graphviz,kbrock/graphviz,kbrock/graphviz,MjAbuz/graphviz,MjAbuz/graphviz,BMJHayward/graphviz,kbrock/graphviz,ellson/graphviz,pixelglow/graphviz,MjAbuz/graphviz,BMJHayward/graphviz,BMJHayward/graphviz,MjAbuz/graphviz,tkelman/graphviz,pixelglow/graphviz,kbrock/graphviz,tkelman/graphviz,BMJHayward/graphviz,ellson/graphviz,pixelglow/graphviz,tkelman/graphviz,jho1965us/graphviz,BMJHayward/graphviz,BMJHayward/graphviz,jho1965us/graphviz,kbrock/graphviz,ellson/graphviz,ellson/graphviz,MjAbuz/graphviz,pixelglow/graphviz,BMJHayward/graphviz,tkelman/graphviz,tkelman/graphviz,jho1965us/graphviz,MjAbuz/graphviz,tkelman/graphviz,kbrock/graphviz,tkelman/graphviz,pixelglow/graphviz,ellson/graphviz,BMJHayward/graphviz,BMJHayward/graphviz,tkelman/graphviz,jho1965us/graphviz,MjAbuz/graphviz,ellson/graphviz,ellson/graphviz,ellson/graphviz,ellson/graphviz,jho1965us/graphviz,kbrock/graphviz,tkelman/graphviz,jho1965us/graphviz,pixelglow/graphviz,tkelman/graphviz,jho1965us/graphviz,MjAbuz/graphviz,pixelglow/graphviz,ellson/graphviz,pixelglow/graphviz,jho1965us/graphviz,kbrock/graphviz