"implement" getnetbyaddr and getnetbyname

these are useless legacy functions but some old software contains
cruft that expects them to exist...

src/network/netname.c

+#include <netdb.h>
+
+struct netent *getnetbyaddr(uint32_t net, int type)
+{
+	return 0;
+}
+
+struct netent *getnetbyname(const char *name)
+{
+	return 0;
+}
+