smbldap: expose bind callback via API and increase smbldap ABI version

smbldap: expose bind callback via API and increase smbldap ABI version

Until we fully migrate to use gensec in smbldap, we need to continue
exposing bind callback to allow FreeIPA to integrate with smbldap.

Since smbldap API is now lacking direct access to 'struct
smbldap_state' and new API functions were added to give access to
individual members of this structure, it makes sense to increase ABI
version too.

Signed-off-by: Alexander Bokovoy <ab@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Tue Jul  4 11:14:49 CEST 2017 on sn-devel-144