wxItemContainer add more methods for selection, add some to RadioBox too
because it can't include directly
add helper function for style flags in initialize methods. its main
purpose is for "style |= wxCONSTANT"
wxRadioButton: use the new set_hash_flag_option
wxTextCtrl: use new set_hash_flag_option
wxPropertyGridManager: use new set_hash_flag_option
wxChoice: add new set_hash_flag_option, and add Style Constants
wxListBox: use new set_hash_flag_option and add Style Constants
wxItemContainer: add sorted? and item_count functions
wxSizer: add flag for border: specific flags will added later
wxDirDialog: use new set_hash_flag_option