Fix an annoying compiler warning on MSVC

Fix a warning about truncating a const through a static_cast
on MSVC.

Change-Id: I381ce806d602c006ef6f14eb4fc89716bc5403ae
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

src/corelib/tools/qversionnumber.h

@@ -387,7 +387,7 @@ public:
     }
 
 private:
-    enum { SegmentUnknown = static_cast<quint8>(~0U) };
+    enum { SegmentUnknown = 0xff };
 
 #if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
     constexpr QTypeRevision(quint8 major, quint8 minor)