Patch by Moshe:

- comment.module: fixed an ambigous 'timestamp' query

- forum.module: prev/next links no longer excerpt from the title+body in
their title attribute. they now excerpt from only their title. this is
more consistent with rest of drupal, and GROUP BY on node.body which
isn't appreciated by MSSQL. also replaced some '' with NULL which caused
errors in MSSQL

- statistics.module: replaced a USING join with a standard ON join. USING
is not as widely supported, and functionally equivalent.