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*

include/wx/qt/private/winevent.h

@@ -54,7 +54,7 @@ public:
         : Widget( parent != NULL ? parent->GetHandle() : NULL )
         , wxQtSignalHandler< Handler >( handler )
     {
-        // Set immediatelly as it is used to check if wxWindow is alive
+        // Set immediately as it is used to check if wxWindow is alive
         wxWindow::QtStoreWindowPointer( this, handler );
 
         // Handle QWidget destruction signal AFTER it gets deleted