attempt to regularize atoi mess.

coreutils/diff.c

@@ -1192,7 +1192,7 @@ int diff_main(int argc, char **argv)
 
 	context = 3;		/* This is the default number of lines of context. */
 	if (cmd_flags & FLAG_U) {
-		context = bb_xgetlarg(U_opt, 10, 1, INT_MAX);
+		context = xatoul_range(U_opt, 1, INT_MAX);
 	}
 	argc -= optind;
 	argv += optind;