Mark modified hotkeys in the hotkey editor

THis uses a simple " *" suffix, as the wxTreeListCtrl-derivative
widget doesn't allow easy access to things like font style.

common/widgets/widget_hotkey_list.cpp

@@ -308,10 +308,17 @@ void WIDGET_HOTKEY_LIST::UpdateFromClientData()
 
         if( hkdata )
         {
-            const EDA_HOTKEY& hk = hkdata->GetChangedHotkey().GetCurrentValue();
+            const auto& changed_hk = hkdata->GetChangedHotkey();
+            const EDA_HOTKEY& hk = changed_hk.GetCurrentValue();
+
+            wxString key_text = KeyNameFromKeyCode( hk.m_KeyCode );
+
+            // mark unsaved changes
+            if( changed_hk.HasUnsavedChange() )
+                key_text += " *";
 
             SetItemText( i, 0, wxGetTranslation( hk.m_InfoMsg ) );
-            SetItemText( i, 1, KeyNameFromKeyCode( hk.m_KeyCode ) );
+            SetItemText( i, 1, key_text);
         }
     }
 }

include/hotkey_store.h

@@ -71,6 +71,15 @@ public:
         m_orig = m_changed;
     }
 
+    /**
+     * @brief Return true if the hotkey doesn't match the original (i.e. it
+     * has been changed)
+     */
+    bool HasUnsavedChange() const
+    {
+        return m_orig.m_KeyCode != m_changed.m_KeyCode;
+    }
+
     const wxString& GetSectionTag() const
     {
         return m_tag;