Bugzilla 912964 - bug in handling of LDAPv3 control data
    
    Bug Description:
    If we receive an incorrect control, with non NULL bv_val but
    bv_len=0, it can trigger a crash.  This bug occurs because
    of a call of openldap ber_init with such incorrect control.
    
    Fix Description:
    Before calling ber_init, check that the control lenght is not 0.
    
    Note: checking in the patch on behalf of "Thierry bordaz"
    <tbordaz@redhat.com>
    
    https://bugzilla.redhat.com/show_bug.cgi?id=913228
    
    Reviewed by: rmeggins@redhat.com, nhosoi@redhat.com
    
    Platforms tested: Fedora 18, RHEL 6.4 (RHDS6.4)
    
    Flag Day: no
    
    Doc impact: possibly document a security bug