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/propgrid/propgridiface.h

@@ -540,7 +540,7 @@ public:
 
     // Hides or reveals a property.
     // hide - If true, hides property, otherwise reveals it.
-    // flags - By default changes are applied recursively. Set this paramter
+    // flags - By default changes are applied recursively. Set this parameter
     //   wxPG_DONT_RECURSE to prevent this.
     bool HideProperty( wxPGPropArg id,
                        bool hide = true,