shims: correct `TAILQ_CONCAT`
This fixes libdispatch on Windows where we use the shims rather than a
system provided `sys/queue.h` as that is a BSD extension.
#define TAILQ_CONCAT(head1, head2, field) do { \
if (!TAILQ_EMPTY(head2)) { \
(head1)->tq_last = (head2)->tq_first; \
- (head1)->tq_first->field.te_prev = (head1)->tq_last; \
+ (head2)->tq_first->field.te_prev = (head1)->tq_last; \
(head1)->tq_last = (head2)->tq_last; \
TAILQ_INIT((head2)); \
} \
