Add support for pseudo IP/TCP/UDP checksums.

Most NIC cards support checksum offloading,
meaning that it is not necessary to calculate the
full IP/TCP/UDP checksums for injected packets.
WINDIVERT_ADDRESS has been extended to include 3
extra flags that indicate if the packet has full
or pseudo checksums.  This is a WIP.

examples/netdump/netdump.c

@@ -124,10 +124,6 @@ int __cdecl main(int argc, char **argv)
             continue;
         }
 
-        // Calculate checksums.
-        WinDivertHelperCalcChecksums(packet, packet_len,
-            WINDIVERT_HELPER_NO_REPLACE);
-       
         // Print info about the matching packet.
         WinDivertHelperParsePacket(packet, packet_len, &ip_header,
             &ipv6_header, &icmp_header, &icmpv6_header, &tcp_header,