debugger: make the selection of detach or kill explicit

Change-Id: I6f80047ad229e0be851b06a277ab2f899757828f
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/debugger/gdb/gdbengine.h

@@ -264,7 +264,6 @@ private: ////////// Gdb Process Management //////////
     void handleNamespaceExtraction(const GdbResponse &response);
 
     void handleAdapterStarted();
-    void defaultInferiorShutdown(const char *cmd);
     void loadInitScript();
     void loadPythonDumpers();
     void pythonDumpersFailed();