debugger: show vtable ptr in hex, also with gdb

Task-number: QTCREATORBUG-6109
Change-Id: I9df2ddcd47e3551b23af20d2199b45fbee34bf9f
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/debugger/watchdata.h

@@ -93,6 +93,7 @@ public:
     bool isLocal()   const { return iname.startsWith("local."); }
     bool isWatcher() const { return iname.startsWith("watch."); }
     bool isValid()   const { return !iname.isEmpty(); }
+    bool isVTablePointer() const;
 
     bool isEqual(const WatchData &other) const;