Fix warning about not enough actual parameters for macro.

QT_METATYPE_INTERFACE_INIT_EMPTY_DATASTREAM_IMPL ignores arguments
anyway so it is not a problem to give a void type.

Change-Id: I66109cc9ae43b48d5cacbd11bebe135a71e10ed7
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qmetatype_p.h

@@ -183,7 +183,7 @@ public:
 { \
     /*creator*/ 0, \
     /*deleter*/ 0, \
-    QT_METATYPE_INTERFACE_INIT_EMPTY_DATASTREAM_IMPL() \
+    QT_METATYPE_INTERFACE_INIT_EMPTY_DATASTREAM_IMPL(void) \
     /*constructor*/ 0, \
     /*destructor*/ 0, \
     /*size*/ 0, \