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/IXDNSLookup.cpp

@@ -27,7 +27,7 @@ namespace ix
         _done(false),
         _id(_nextId++)
     {
-
+        initNetSystem();
     }
 
     DNSLookup::~DNSLookup()
@@ -137,6 +137,11 @@ namespace ix
             return nullptr;
         }
 
+        if (!_errMsg.empty())
+        {
+            errMsg = _errMsg;
+        }
+
         std::unique_lock<std::mutex> rlock(_resMutex);
         return _res;
     }