Review Request: Add possibility to store Decorators for class- and function declarations

[David Nolden]

Btw. the syntax for multiple appended-lists (copied from pp_macro) is:

START_APPENDED_LISTS(pp_macro)
APPENDED_LIST_FIRST(pp_macro, IndexedString, definition)
APPENDED_LIST(pp_macro, IndexedString, formals, definition)
END_APPENDED_LISTS(pp_macro, formals)

You can add as many lists as you want, just make sure to link from
each to the previous in the last parameter.