Bug 619623 - attr-unique-plugin ignores requiredObjectClass on modrdn operations
    
    The attribute uniqueness plug-in is not checking if renamed entries
    meet the requiredObjectClass requirements.  In addition, a rename
    that uses a new superior is not properly handled.
    
    This patch adds a check for requiredObjectClass for MODRDN ops.  I
    also added a helper function called slapi_entry_rename() which allows
    the caller to apply a MODRDN operation to a Slapi_Entry.  My patch
    makes use of this to create a renamed dummy entry that is used to
    check for any attribute uniqueness conflicts.