Explicite TypeCast for searchIndex

Running the /bin/indexer.php or the searchindex plugin fails in php5
with several type cast errors. This can be fixed using explicite type casts.

Secondly the include plugin requires the auth.php to be present. As some other
plugins might use quick-acl or the $auth too, indexer.php should require the auth.php
just as the lib/exe/indexer.php does.

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