BUILD: kqueue/threads: Add test on MAX_THREADS to avoid warnings when complied without threads

This is the same patch than the previous one ("BUILD: epoll/threads: Add test on
MAX_THREADS to avoid warnings when complied without threads ").

It should be backported in 1.8 with the commit 7a2364d4 ("BUG/MEDIUM:
kqueue/threads: use one kqueue_fd per thread").
1 file changed