restore building --test-build-rtsig and --test-build-eventport on FreeBSD 6

src/event/modules/ngx_eventport_module.c

diff --git a/src/event/modules/ngx_eventport_module.c b/src/event/modules/ngx_eventport_module.c
index f9a8e88..4becf75 100644
--- a/src/event/modules/ngx_eventport_module.c
+++ b/src/event/modules/ngx_eventport_module.c
@@ -40,6 +40,15 @@
     void       *portnfy_user;   /* user defined */
 } port_notify_t;
 
+#if (__FreeBSD_version < 700005)
+
+typedef struct itimerspec {     /* definition per POSIX.4 */
+    struct timespec it_interval;/* timer period */
+    struct timespec it_value;   /* timer expiration */
+} itimerspec_t;
+
+#endif
+
 int port_create(void)
 {
     return -1;

src/event/modules/ngx_rtsig_module.c

diff --git a/src/event/modules/ngx_rtsig_module.c b/src/event/modules/ngx_rtsig_module.c
index c753854..6020936 100644
--- a/src/event/modules/ngx_rtsig_module.c
+++ b/src/event/modules/ngx_rtsig_module.c
@@ -11,8 +11,14 @@
 
 #if (NGX_TEST_BUILD_RTSIG)
 
-#define F_SETSIG       10
+#ifdef  SIGRTMIN
 #define si_fd          _reason.__spare__.__spare2__[0]
+#else
+#define SIGRTMIN       33
+#define si_fd          __spare__[0]
+#endif
+
+#define F_SETSIG       10
 #define KERN_RTSIGNR   30
 #define KERN_RTSIGMAX  31