Curl_llist_init is never used outside of llist.c and thus it should be
static. I also removed the protos for Curl_llist_insert_prev and
Curl_llist_remove_next which are functions we removed from llist.c ages
ago.
previously had a number of flaws, perhaps most notably when an application
fired up N transfers at once as then they wouldn't pipeline at all that
nicely as anyone would think... Test case 530 was also updated to take the
improved functionality into account.
Daniel Stenberg