An editor previewing a page using too many parser functions is warned "Warning: This page contains too many expensive parser function calls", and the page is put in a maintenance category.
This is not the case when you include too many templates in a page/use too long template arguments. Of course, one can dig into the HTML source, but that is not really user-friendly.
This patch tries to handle that issue, adding two more warning messages, and two more maintenance categories.
I'd like some more experienced users to review it so that I can commit it :)