HEADS UP: connections are forced to "anonymous" status upon receiving

HEADS UP:  connections are forced to "anonymous" status upon receiving
of a bind request and, upon failure, are left "anonymous."

Rework ACL code to hide access testing within macros to facilate additions
and eventual redesign.

Addition of #ifdef SLAPD_ACLAUTH to conditional include EXPERIMENTAL
"auth" access controls.  Adds ACL_AUTH "auth" access level (above none,
below "compare").  bind requires anonymous access at this level or above access
to "entry"/"userPassword"/"krbName".  This allows administrators to restrict
which entries can be bound to.  (This will likely become default behavior
after testing has completed).