Debugger: Rework thread data aquisition

Listen to gdb/MI notifications when possible. This is more
granular, gives access to the thread group id and takes
care of thread changes at any time.

Change-Id: I8c67f6f19b204059deefdf7e07fe3b4ce13ed963
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

src/plugins/debugger/debuggerengine.cpp

@@ -1233,10 +1233,6 @@ void DebuggerEngine::setState(DebuggerState state, bool forced)
             handler->notifyBreakpointReleased(id);
     }
 
-    const bool running = d->m_state == InferiorRunOk;
-    if (running)
-        threadsHandler()->notifyRunning();
-
     showMessage(msg, LogDebug);
     updateViews();
 
@@ -1586,10 +1582,6 @@ void DebuggerEngine::changeBreakpoint(BreakpointModelId id)
     QTC_CHECK(false);
 }
 
-void DebuggerEngine::selectThread(int)
-{
-}
-
 void DebuggerEngine::assignValueInDebugger(const WatchData *,
     const QString &, const QVariant &)
 {