accesslib: remove some functions we do not need anymore

accesslib: remove some functions we do not need anymore

This is *the* scary commit. No more scaffolding, no more
training wheels. Remove the legacy has_capabilty_old() and
several supporting functions.

   has_capability_old()
   capability_search()
   is_parent_context()
   roles_context_cmp()
   load_user_capability()
   capability_prohibits()

I've grepped far and wide. Noone else uses the supporting
functions anywhere in-the-known-universe. If I could not
find it, it does not exist.

[Thankful that cvs/git/whatever will hold on to them
 if I end up having to regret this.]