Add a new internal LDAP socket implementation that provides a mechanism which
allows third-party LDAP SDKs to be used to perform internal operations within
the server.  Rather than performing network communication, the custom socket
decodes the request written to it, converts it to an internal operation,
processes the request, and encodes the response so that it can be read from the
socket by the LDAP SDK.

This has been tested with both the Mozilla LDAP SDK for Java (which requires a
trivial custom LDAPSocketFactory implementation) and JNDI (which requires a
custom property to be set).