builtin export fixed and refactored

+ builtin exit, env verif OK

srcs/builtins/unset.c

@@ -35,7 +35,7 @@ int	builtin_unset(int argc, char *argv[], t_all *c)
 static int	unset_env_var(char *arg)
 {
 	int	env_position;
-	
+
 	if (!ft_is_posix_name(arg))
 	{
 		shell_error("unset: ", arg, ": not a valid identifier", 0);