Introducing the shared application port.

This is the port shared between all application processes which use it to pass
requests for processing.  Using it significantly simplifies the request
processing code in the router.  The drawback is 2 more file descriptors per each
configured application and more complex libunit message wait/read code.

go/port.go

@@ -93,7 +93,7 @@ func getUnixConn(fd int) *net.UnixConn {
 }
 
 //export nxt_go_add_port
-func nxt_go_add_port(pid C.int, id C.int, rcv C.int, snd C.int) {
+func nxt_go_add_port(ctx C.uintptr_t, pid C.int, id C.int, rcv C.int, snd C.int) {
 	p := &port{
 		key: port_key{
 			pid: int(pid),
@@ -104,6 +104,12 @@ func nxt_go_add_port(pid C.int, id C.int, rcv C.int, snd C.int) {
 	}
 
 	add_port(p)
+
+	if id == 65535 {
+		go func(ctx C.uintptr_t) {
+			C.nxt_cgo_unit_run_shared(ctx);
+		}(ctx)
+	}
 }
 
 //export nxt_go_remove_port