using best available mechanism.  (authzid prompting to be disabled)
To use simple bind, -x is required (implied if -P 2) with -D/-[Ww]
To use simple "anonymous" bind, just -x will do.

Add additional notices.  Likely need to add a quiet mode.

(used by clients/tools/ldap*.c)

Replace 'negotiated' with 'interactive' bind
Add hooks for SASL/EXTERNAL
Disable SASL security layers
Rework SASL command line and config file parameters

s/LDAP_PF_UNIX/LDAP_PF_LOCAL/
s/AF_UNIX/AF_LOCAL/
s/PF_UNIX/PF_LOCAL/

based upon patch provided by Ted C. Cheng <cheng@ix.netcom.com>

strerror() as strerror() may not be thread safe.  Likely should
be used by SLAPD.

And some code cleanup.