Use the correct modern windows sockets header

As suggested in a PR from @Legend-Master (this change is basically
unrelated to the main point of his PR, so extracted here)

Windows is a confusing and disappointing development environment.  They
completely replaced all the definitions in winsock.h with exact
equivalents in winsock2.h (except for a small number of deprecated
functions).

However they didnt make them mutually exclusive - so if you include
both, you get errors.  They also automatically include winsock.h from
windows.h, so you must remember to include winsock2.h first.  They also
didnt just remove winsock.h and replace it with the new contents.

(Probably in the name of "compatibility", whilst swearing that the new
winsock is the same as the old one - because if you cannot believe two
inconsistent things simultaneously, you shouldnt be a windows
programmer)

All these things are totally nuts.  Thanks, windows dev environment,
for not noticing that this is nuts

include/n2n.h

@@ -56,11 +56,11 @@
 #include "n2n_typedefs.h"
 
 #ifdef WIN32
+#include <winsock2.h>           /* for tcp */
 #include <lmaccess.h>           /* for privilege check in tools/n2n-route */
 #include <lmapibuf.h>           /* for privilege check in tools/n2n-route */
 #include <sys/stat.h>
 #include <windows.h>            /* for privilege check in tools/n2n-route */
-#include <winsock2.h>           /* for tcp */
 #include "wintap.h"
 #define SHUT_RDWR   SD_BOTH     /* for tcp */
 #endif /* #ifdef WIN32 */

src/edge.c

@@ -43,7 +43,7 @@
 #include "uthash.h"                  // for UT_hash_handle, HASH_ADD, HASH_C...
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #include <ws2tcpip.h>
 #else
 #include <arpa/inet.h>               // for inet_addr, inet_ntop

src/edge_management.c

@@ -36,7 +36,7 @@
 #include "uthash.h"        // for UT_hash_handle, HASH_ITER
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #include <ws2tcpip.h>
 #include "edge_utils_win32.h"
 #else

src/edge_utils.c

@@ -41,7 +41,7 @@
 #include "uthash.h"                  // for UT_hash_handle, HASH_COUNT, HASH...
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #include <ws2tcpip.h>
 #include "edge_utils_win32.h"
 #else

src/example_sn_embed.c

@@ -22,7 +22,7 @@
 #include "n2n.h"         // for n2n_sn_t, open_socket, run_sn_loop, sn_init
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #else
 #include <netinet/in.h>  // for INADDR_ANY, INADDR_LOOPBACK
 #endif

src/management.h

@@ -17,7 +17,7 @@
 #include "strbuf.h"
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #else
 #include <sys/socket.h>    // for sockaddr, sockaddr_storage, socklen_t
 #endif

src/n2n.c

@@ -31,7 +31,7 @@
 #include "uthash.h"          // for UT_hash_handle, HASH_DEL, HASH_ITER, HAS...
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #include <ws2def.h>
 #include <ws2tcpip.h>
 #else

src/network_traffic_filter.c

@@ -26,7 +26,7 @@
 #include "uthash.h"                  // for UT_hash_handle, HASH_ITER, HASH_DEL
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #include <ws2tcpip.h>
 #else
 #include <arpa/inet.h>               // for inet_ntoa, inet_addr

src/sn_management.c

@@ -36,7 +36,7 @@
 #include "uthash.h"      // for UT_hash_handle, HASH_ITER, HASH_COUNT
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #include "edge_utils_win32.h"
 #else
 #include <sys/socket.h>  // for sendto, socklen_t

src/sn_utils.c

@@ -41,7 +41,7 @@
 #include "uthash.h"             // for UT_hash_handle, HASH_ITER, HASH_DEL
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #include <ws2tcpip.h>
 #else
 #include <arpa/inet.h>          // for inet_addr, inet_ntoa

src/supernode.c

@@ -36,7 +36,7 @@
 #include "uthash.h"            // for UT_hash_handle, HASH_ITER, HASH_ADD_STR
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #include <ws2tcpip.h>
 #else
 #include <arpa/inet.h>         // for inet_addr

src/wire.c

@@ -34,7 +34,7 @@
 #include "n2n_wire.h"    // for decode_PACKET, decode_PEER_INFO, decode_QUER...
 
 #ifdef WIN32
-#include <winsock.h>
+#include <winsock2.h>
 #include <ws2tcpip.h>
 #else
 #include <netinet/in.h>  // for sockaddr_in, sockaddr_in6, in6_addr, in_addr