fix case of included header file

case mismatch was causing cmake and ccache to never find the dependency
and resulted in always rebuilding the file, even if nothing had changed

Author: myk002

src/SimpleSocket.h

@@ -76,7 +76,7 @@
 #ifdef _WIN32
 #include <io.h>
 #include <winsock2.h>
-#include <Ws2tcpip.h>
+#include <ws2tcpip.h>
 
 #define IPTOS_LOWDELAY  0x10