Not hidden "NULLDN" to "<anonymous>" in modify stats

(basically, it's for testing internals, don't enable it otherwise)

suggested by Steve Sonntag.

Not hidden: "<anonymous>" modifiersname

plus these changes unhidden changes:
	remove now meaning --enable-discreteaci configure option
	fix ITS#451, slapd filters
	Add ber_bvecadd() to support above
	constify ldap_pvt_find_wildcard() and misc slapd routines
	renamed some slap.h macros
	likely broken something

Only user can select appropriate run directory.  Best left to user.

Changes outside of #ifdef include three value filter processing.

basic structures for handing language tags and binary option
(but less actual code to actually support them).  Provided
for reference only.  Will not even compile.

Use BASE64 if attr-desc includes ";binary"

implement an at_exit() handler.

wrong. Fix from adamson@andrew.cmu.edu.

additional schema items.

OID for experimental syntax.

Noticed that abandon and unbind don't have control support... something for
another day.

rewrite.

Attribute subtyping, especially that using attribute description
options, will have to reengineered.

attributes of the syntax.  Such attribute values be transferred
using binary syntax unless ber2str/str2ber routines are provided.
Used in conjunction with ";binary" attribute description option
and/or the Binary syntax.

filters.

routines to separate file to keep schema.c of managable size.