Add normalized dn to Entry structure as field e_ndn. Entry

Add normalized dn to Entry structure as field e_ndn.  Entry
creation codes to provide this field.  Update cache_entrydn_cmp
to strcasecmp() the e_ndn instead of e_dn.  Note: strcasecmp()
is still used as e_ndn isn't in uppercase.  Maybe it should
be.  Did not update other codes to use e_ndn.  Hence, there
are lots of dn_normalize() calls that could be eliminated.
(The case determination of e_ndn should be made first).