Create a D5 -> D6 upgrade path

This is not a very nice "welcome to Drupal 6!" ;)

As you can see, <!--paging_filter--> is being displayed everywhere we're using Full/Filtered HTML. Keyz @ http://drupal.org/node/179456#comment-631446 correctly identified the cause of the error in our case: the weight of HTML corrector is later than Paging. This happens specifically in the D5 -> D6 upgrade path because it's a new filter and core sticks it at the bottom of the list.

It seems this could be readily solved by writing an upgrade path to change the weight of the Paging filter to +1 HTML corrector's weight in each input format it's found in. Patch forthcoming sometime over the weekend.

There are a few places where this has already been reported, such as #179456: <!--paging_filter--> not removed from HTML output and #433604: The garbage in displayed code, but those issues get a bit tangled up in the various ways you can get configuring input formats wrong. The scope of this issue is just fixing the upgrade path, so this specific problem doesn't bite anyone else.