Debugger: Make display of QObject names optional

... and switch it off by default. The feature has indeterministic
performance impact and lost quite a bit of its utility since GDB
learned to extract dynamic object types most of the times.

Change-Id: I22cccb03ba67f9ff6ad757bbc06eb372d84bbffe
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@theqtcompany.com>
Reviewed-by: hjk <hjk@theqtcompany.com>

src/plugins/debugger/debuggeractions.h

@@ -157,6 +157,7 @@ enum DebuggerActionCode
     // Watchers & Locals
     ShowStdNamespace,
     ShowQtNamespace,
+    ShowQObjectNames,
     SortStructMembers,
     AutoDerefPointers,
     MaximalStringLength,