chat: - remove table-based renderer for polled mode; we use now always (in polled, streaming and scripted-streaming mode) div-based message layout - extend ::xowiki::Chat login by an option "-path" to make sharing of ajax-files simpler in derived packages (e.g. xowf)
- Added the changes mostly provided by Antonio Pisano to update the comet behavior for current browsers, which provide nowadays often more complete HTTP stacks.