Description: When Simple Paged Results is requested and a page is
returned, one entry is read ahead to check whether more entries
exist or not. The read-ahead retrieves an entry (if any) and adds
it into the entry cache. Simple Paged Results code puts the read-
ahead entry back, but there was missing to call cache_return for
the entry (that decrementing refcnt). If ldif2db.pl is called with
the cache state, it finds out the entry which is still referred.
This patch calls cache_return when the Simple Paged Results puts
the read-ahead entry back. Plus, adding a debug function dump_hash.