Semantic seems to know what #ifdef regions are enabled, and emacs has a
command to shadow or hide a given #ifdef region.
Is it possible to have semantic call hide-ifdef-block appropriately for
each #ifdef in a file? or write a function to do so?
If that's hard.. would it be easier to write a function to go to the end
of the file, get a list of all defined symbols, then call
hide-ifdef-define or hide-ifdef-define-alist appropriately?