Perform a nested include of _label.h if #ifdef _KERNEL. This will

satisfy consumers of ip_var.h that need a complete definition of
struct ipq and don't include mac.h.

Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, NAI Labs

sys/netinet/ip_var.h

@@ -39,6 +39,10 @@
 
 #include <sys/queue.h>
 
+#ifdef _KERNEL
+#include <sys/_label.h>
+#endif
+
 /*
  * Overlay for ip header used by other protocols (tcp, udp).
  */