add code to open (display) debug.log on Windows with the associated application and add a button to the Information page in the Debug console

src/qt/guiutil.h

@@ -70,6 +70,9 @@ namespace GUIUtil
     // Determine whether a widget is hidden behind other windows
     bool isObscured(QWidget *w);
 
+    // Open debug.log
+    void openDebugLogfile();
+
     /** Qt event filter that intercepts ToolTipChange events, and replaces the tooltip with a rich text
       representation if needed. This assures that Qt can word-wrap long tooltip messages.
       Tooltips longer than the provided size threshold (in characters) are wrapped.