misc/143033: _SWAP not listed in comment in sys/queue.h

[Jeremy Huddleston]

Please ignore my previous comment about the non-existent  
TAILQ_REMOVE_AFTER, but the point remains that _SWAP is not mentioned  
in queue(3).

     LIST_SWAP(LIST_HEAD *head1, LIST_HEAD *head2, TYPE, LIST_ENTRY  
NAME)
     STAILQ_SWAP(STAILQ_HEAD *head1, STAILQ_HEAD *head2, TYPE);
     TAILQ_SWAP(TAILQ_HEAD *head1, TAILQ_HEAD *head2, TYPE,  
TAILQ_ENTRY NAME)