We now pass a pointer to the context where necessary. There are a
few cases where we need to request the context from sudoers via
sudoers_get_context() for the plugin API functions. If the plugin
API was able to pass around a closure pointer this would not be
necessary.
o The parse tree is now passed to the alias, match and defaults functions.
o The nss API has been changed so that the nss parse() function returns
a pointer to a struct sudoers_parse_tree which will be filled in
by the getdefs() and query() functions.
in a per-nss list of userspecs and defaults instead of using separate
lookup and list functions. This makes it possible to have a single
implementation of the code for sudoers lookup and listing.
queue functions. This includes a private queue.h header derived
from FreeBSD. It is simpler to just use our own header rather than
try to deal with macros that may or may not be present in various
queue.h incarnations.
