activex: snprintf is defined in stdio.h, include it

This applies for plugin.cpp, vlccontrol2.cpp and persistpropbag.
Signed-off-by: Rémi Denis-Courmont <rdenis@simphalempin.com>

projects/activex/persistpropbag.h

@@ -23,6 +23,7 @@
 #ifndef __PERSISTPROPBAG_H__
 #define __PERSISTPROPBAG_H__
 
+#include <stdio.h>
 #include <ocidl.h>
 
 class VLCPersistPropertyBag : public IPersistPropertyBag

projects/activex/plugin.cpp

@@ -40,6 +40,7 @@
 
 #include "utils.h"
 
+#include <stdio.h>
 #include <string.h>
 #include <winreg.h>
 #include <winuser.h>

projects/activex/vlccontrol2.cpp

@@ -27,6 +27,7 @@
 
 #include "utils.h"
 
+#include <stdio.h>
 #include <shlwapi.h>
 #include <wininet.h>
 #include <tchar.h>