Fix crash in res_config_ldap.

We need to allocate enough room for 2 pointers, not 2 characters.

(closes issue #16397)
Reported by: bklang
Patches:
      res_config_ldap.patch uploaded by applsplatz (license 949)
Tested by: applsplatz


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@239473 65c4cc65-6c06-0410-ace0-fbb531ad65f3