Fixes for windows (#45)

* init Net system on Windows

* propagate DNS error

* Add zlib 1.2.11 sources

* link zlib statically for windows

* remove not implemented function declaration

* fix connect on Windows

ixwebsocket/IXNetSystem.cpp

@@ -0,0 +1,39 @@
+/*
+ *  IXNetSystem.cpp
+ *  Author: Benjamin Sergeant
+ *  Copyright (c) 2019 Machine Zone. All rights reserved.
+ */
+
+#include "IXNetSystem.h"
+
+namespace ix
+{
+    bool initNetSystem()
+    {
+#ifdef _WIN32
+        WORD wVersionRequested;
+        WSADATA wsaData;
+        int err;
+
+        /* Use the MAKEWORD(lowbyte, highbyte) macro declared in Windef.h */
+        wVersionRequested = MAKEWORD(2, 2);
+
+        err = WSAStartup(wVersionRequested, &wsaData);
+
+        return err == 0;
+#else
+        return true;
+#endif
+    }
+
+    bool uninitNetSystem()
+    {
+#ifdef _WIN32
+        int err = WSACleanup();
+
+        return err == 0;
+#else
+        return true;
+#endif
+    }
+}