Add unsigned char cast to isdigit

lib/libc/gen/disklabel.c

@@ -171,7 +171,7 @@ gettype(t, names)
 	for (nm = names; *nm; nm++)
 		if (strcasecmp(t, *nm) == 0)
 			return (nm - names);
-	if (isdigit(*t))
+	if (isdigit((unsigned char)*t))
 		return (atoi(t));
 	return (0);
 }

lib/libc/gen/setmode.c

@@ -204,7 +204,7 @@ setmode(p)
 	 * If an absolute number, get it and return; disallow non-octal digits
 	 * or illegal bits.
 	 */
-	if (isdigit(*p)) {
+	if (isdigit((unsigned char)*p)) {
 		perm = (mode_t)strtol(p, NULL, 8);
 		if (perm & ~(STANDARD_BITS|S_ISTXT)) {
 			free(saveset);