Fixed sockets ext build on win

ext/sockets/multicast.c

@@ -38,6 +38,9 @@
 # define NTDDI_XP NTDDI_WINXP /* bug in SDK */
 # include <IPHlpApi.h>
 # undef NTDDI_XP
+# if _WIN32_WINNT >= 0x0600
+#  define HAVE_IF_NAMETOINDEX 1
+# endif
 #else
 #include <sys/socket.h>
 #include <sys/ioctl.h>

ext/sockets/sockets.c

@@ -57,6 +57,7 @@
 # define h_errno		WSAGetLastError()
 # define set_errno(a)		WSASetLastError(a)
 # define close(a)		closesocket(a)
+# include <IPHlpApi.h>
 # if _WIN32_WINNT >= 0x0600
 #  define HAVE_IF_NAMETOINDEX 1
 # endif