(ITS#7301) Improve DNS SRV support in OpenLDAP

[quanah@OpenLDAP.org]

Full_Name: Quanah Gibson-Mount
Version: 2.4.31
OS: 
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (75.108.184.39)


LDAP URI handling via SRV records is not in the library. In
particular, an OpenLDAP library client that specifies a
(correctly formed or otherwise) LDAP URI of the form:

	ldap:///dc=example,dc=com/

will not be connected to the LDAP servers found in the SRV records
for _ldap._tcp.example.com. That code is only in the ldapsearch(1)
and related tools.

The existence of the low-level support functions in the library is
of no help to users who want to specify URIs that resolve to the
underlying LDAP servers via SRV records.

Also, the SRV -> host:port list lookup code that is in the library
(but not tied to the libraries connection establishment code) is
broken, it ignores the weight and priority which is not a good
idea, the published SRV priorities and weights must not be ignored.