Add a missing header and remove an unused variable.

ndhc/dhcpmsg.c

@@ -222,7 +222,6 @@ int get_raw_packet(struct dhcpMessage *payload, int fd)
 {
     struct ip_udp_dhcp_packet packet;
     uint16_t check;
-    const int header_size = sizeof(struct iphdr) + sizeof(struct udphdr);
     const int packet_size = sizeof(struct ip_udp_dhcp_packet);
 
     memset(&packet, 0, packet_size);

ndhc/socket.c

@@ -26,6 +26,7 @@
 #include <sys/ioctl.h>
 #include <netinet/in.h>
 #include <unistd.h>
+#include <fcntl.h>
 #include <string.h>
 #include <arpa/inet.h>
 #include <net/if.h>