Modify fd_add_to_fd_list() and fd_rm_from_fd_list() so that they take an offset in the fdtab to the list entry, instead of hardcoding the fd cache, so we can use them with other lists.
Modify fd_add_to_fd_list() and fd_rm_from_fd_list() so that they take an offset in the fdtab to the list entry, instead of hardcoding the fd cache, so we can use them with other lists.