Fix spelling in comments and documentation using codespell

Apply the utility from https://github.com/codespell-project/codespell/
to fix spelling issues in the headers under both include and interface
directories and add a file with a couple of exceptions.

The exact command line used was:

    $ codespell -w -I misc/scripts/codespell.ignore -i 3 in*

interface/wx/stackwalk.h

@@ -86,7 +86,7 @@ public:
 
 protected:
     /**
-        This function must be overidden to process the given frame.
+        This function must be overridden to process the given frame.
     */
     virtual void OnStackFrame(const wxStackFrame& frame) = 0;
 };