Include Winsock2 header before windows.h include

That's because there are duplicate #defines, and when Winsock2 is defined
before windows.h then windows.h detects that and prevent redefinition.

See
http://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/4a90b143-1fb8-43e9-a54c-956127e0c579/windowsh-and-winsock2h?forum=windowssdk

[JES: fixed commit message]
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

libvncclient/vncviewer.c

@@ -21,6 +21,11 @@
  * vncviewer.c - the Xt-based VNC viewer.
  */
 
+#ifdef WIN32
+#undef SOCKET
+#include <winsock2.h>
+#endif
+
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
 #define _POSIX_SOURCE
@@ -44,8 +49,6 @@ static void DummyRect(rfbClient* client, int x, int y, int w, int h) {
 static char* NoPassword(rfbClient* client) {
   return strdup("");
 }
-#undef SOCKET
-#include <winsock2.h>
 #define close closesocket
 #else
 #include <stdio.h>