Revert to static blocks on disabling the module

It's a bother to replace the static blocks after the module is enabled, but it's even worse to have to reverse this setting when the module is disabled: Instead of displaying the static blocks, the site loses all DHTML blocks immediately without replacement.

A hook_disable function should be added that effectively does the reverse of http://drupal.org/node/188971, in that it reads the placement values of the DHTML blocks and assigns them to the static equivalent blocks. (Obviously, we can omit the disabling of the DHTML blocks as they will be removed anyway.)

It's not a critical issue, but I believe this should be backported to 5.x so I mark it as a bug.