LcdSpinBox: check for mouse button in mouseReleaseEvent()

Otherwise we restore things that were never changed when releasing right
or middle mouse button.

Closes #358.

include/lcd_spinbox.h

@@ -72,6 +72,7 @@ protected:
 	virtual void wheelEvent( QWheelEvent * _we );
 
 private:
+	bool m_mouseMoving;
 	QPoint m_origMousePos;
 	int m_displayOffset;