5218 posix definition of NULL
correct unistd.h and iso/stddef_iso.h
update gate source affected

@@ -354,11 +354,11 @@
                 endseen = numbase64chars = 0;
                 optr = outbuf;
                 while ((fgets(inbuf, sizeof (inbuf), in)) != NULL) {
                         /* process an input line */
                         iptr = inbuf;
-                        while ((curchr = *(iptr++)) != NULL) {
+                        while ((curchr = *(iptr++)) != '\0') {
                                 /* decode chars */
                                 if (curchr == '=') /* if end */
                                         endseen++;
 
                                 if (validbase64(curchr))