Notes on count(DISTINCT item_id) and MySQL versions below 3.23.2
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If you do a search from the search page for 'Reviews', and an item has more than one review 
that matches the search criteria, duplicate items will be returned.

A 'DISTINCT' keyword added to SQL in functions/item.php::fetch_item_listing_rs(...), will
actually ensure that no duplicate records are returned.

Unfortunately this then results in an incorrect $total record count.  The 'Listing Items
{first_row} through {last_row} of {total}' footer will have an incorrect {total} value.

The fix for this is also to add a DISTINCT to the fetch_item_listing_cnt(...) function,
but versions of MySQL below '3.23.2', do not support it!

Solution:

	A new include/config.php variable, $CONFIG_VARS['listings.count_distinct_support'], which 
	when set to FALSE, will execute a separate query on item_attribute/review first to get the
	distinct list of item_id's which will then be passed into the main query as a IN(...) clause.
	Please do not resort to using this unless ABSOLUTELY necessary.

The default for the parameter when not set is TRUE.  Users with MySQL below 3.23.2, should set
it to FALSE!

