Fixed compilation on NetBSD 10. NetBSD 10 changed struct kevent's udata type from "intptr_t" to "void *", similarly to how it is defined on other systems. This breaks compilation, since intptr_t is assumed on NetBSD. Fix is to limit special intptr_t handling to NetBSD versions before 10.0. To simplify testing, relevant definitions are moved from configure to code (which seems to be the right thing anyway).

--- a/src/os/unix/ngx_freebsd_config.h
+++ b/src/os/unix/ngx_freebsd_config.h
@@ -85,6 +85,7 @@
 
 #if (NGX_HAVE_KQUEUE)
 #include <sys/event.h>
+#define NGX_KQUEUE_UDATA_T  (void *)
 #endif