Resurrection/rewrite of CLDAP (RFC1798 Connectionless LDAP).

Compile with -DLDAP_CONNECTIONLESS to use this code.
For slapd, use "-h cldap://" to listen on UDP.
For ldapsearch, use "-H cldap://" to query on UDP.
Client-side support is very minimal:
  no automatic timeout/retries
  no basedn wildcard expansion on results
  no support for specifying multiple servers at once.