Update/drop cruft: LDAP_DEPRECATED, CLDAP, C version

[Hallvard Breien Furuseth <h.b.furuseth@usit.uio.no>]

Some wishes for RE25:

Expose most LDAP_DEPRECATED functions again.  This code is not going
away, or it'd be gone by now after 16 years of deprecation.  I usually
#define LDAP_DEPRECATED anyway.  What's the point of trying to make me
pass 2 extra NULL args to a bunch of functions?  And making a "SASL
bind" function the proper way to do Simple Bind is silly and confusing.
OTOH some depreciation make sense, like ldap_get_values() which returns
char** instead of berval**.

Add --enable-cldap as "experimental".  Add tests and some fixes.  The
CLDAP code isn't going away either, so i seems better to support it
properly.  People are submitting libldap ITSes, but slapd and ldapsearch
usage remain broken.  slapd looks easy to fix, ldapsearch depends on
vestiges of libldap code to ignore Bind requests.  Dunno if I want to
bother tracking that down in libldap or just omit the Bind in
ldapsearch.  Maybe RedHat has a fix.

...or do the opposite, kill LDAP_DEPRECATED and CLDAP.  I hope not, but
that's better than eternally deprecated/code-rotting features.

Kill K&R1 support, i.e. the LDAP_P(()) stuff.  Supposedly the headers
support K&R1, but OpenLDAP-2.0 broke this (ITS#6171).  Nobody has cared
enough to fix it, and I refuse to fix it.

See if we can require C99 to build OpenLDAP, but keep the headers
C90-compliant.  In particular, replace Debug() with a varargs macro,
initially without changing the calls to Debug().  If we get away with
that, we can kill the extra ,0,0,0 arguments to Debug() later so gcc
-Wformat will catch missing/spurious args.

-- 
Hallvard