gui: Expose BitcoinGUI::unsubscribeFromCoreSignals

Move only change that makes unsubscribeFromCoreSignals public. It must be
called if the event loop is not running otherwise core signals handlers
can deadlock.

src/qt/bitcoingui.h

@@ -95,6 +95,9 @@ class BitcoinGUI : public QMainWindow
  */
  bool hasTrayIcon() const { return trayIcon; }
 
+ /** Disconnect core signals from GUI client */
+ void unsubscribeFromCoreSignals();
+
 protected:
  void changeEvent(QEvent *e);
  void closeEvent(QCloseEvent *event);
@@ -184,8 +187,6 @@ class BitcoinGUI : public QMainWindow
 
  /** Connect core signals to GUI client */
  void subscribeToCoreSignals();
- /** Disconnect core signals from GUI client */
- void unsubscribeFromCoreSignals();
 
  /** Update UI with latest network info from model. */
  void updateNetworkState();