Add res_config_ldap for realtime LDAP engine.

(closes issue #5768)
 Reported by: mguesdon
 Patches: 
       res_config_ldap-v0.7.tar.gz uploaded by mguesdon (license 121)
       res_ldap.conf.sample uploaded by suretec (license 70)
       asterisk-v3.1.4.ldif uploaded by suretec (license 70)
       asterisk-v3.1.4.schema uploaded by suretec (license 70)
 Tested by: oej, mguesdon, suretec, cthorner


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@99696 65c4cc65-6c06-0410-ace0-fbb531ad65f3