Split multi-inserted messages into chunks, because an insert query generated by prepareQueueMessageList may exceed the limit of packet size defined by MySQL, when one transaction activate many, many methods. The max size is heuristic, though.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@28426 20353a03-c40f-0410-a6d1-a30d3c3de9de