move poll wrapper on top of select (only used on Windows) to the ix namespace

ixwebsocket/IXNetSystem.h

@@ -13,11 +13,9 @@
 #include <io.h>
 #include <ws2def.h>
 
-// Define our own poll on Windows
+// Define our own poll on Windows, as a wrapper on top of select
 typedef unsigned long int nfds_t;
 
-int poll(struct pollfd* fds, nfds_t nfds, int timeout);
-
 #else
 #include <arpa/inet.h>
 #include <errno.h>
@@ -35,4 +33,6 @@ namespace ix
 {
     bool initNetSystem();
     bool uninitNetSystem();
+
+    int poll(struct pollfd* fds, nfds_t nfds, int timeout);
 } // namespace ix