Add wxMarkupParser::Strip().

This helper function strips all markup tags from the string (and also decodes
the XML entities in it).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67049 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/private/markupparser.h

@@ -136,6 +136,11 @@ public:
     // interpreted as tag opening characters.
     static wxString Quote(const wxString& text);
 
+    // Strip markup from a string, i.e. simply remove all tags and replace
+    // XML entities with their values (or with "&&" in case of "&" to
+    // prevent it from being interpreted as mnemonic marker).
+    static wxString Strip(const wxString& text);
+
 private:
     // Simple struct combining the name of a tag and its attributes.
     struct TagAndAttrs