Fix for building libusb under Linux.

MFC after:	3 days
Sponsored by:	Mellanox Technologies

lib/libusb/libusb_global_linux.h

@@ -77,4 +77,11 @@
 } while (0)
 #endif
 
+#ifndef TAILQ_FOREACH_SAFE
+#define	TAILQ_FOREACH_SAFE(var, head, field, tvar)			\
+	for ((var) = TAILQ_FIRST((head));				\
+	    (var) && ((tvar) = TAILQ_NEXT((var), field), 1);		\
+	    (var) = (tvar))
+#endif
+
 #endif					/* _LIBUSB_GLOBAL_LINUX_H_ */