JIT incorrectly derives the type of HTMLDocument in IE8 (probably IE7 too)

[dcabasson]

This is causing some pain with jquery.spacetree which is not working with IE 8 (possibly same for IE7).

I have written a short fix and will send a pull request if there is interest to integrate that in JIT to better support IE8/7 (yeah, I know kind of backward, but they are still fairly present with the users, and I need to support them).

[philogb]

I'll happily integrate it, as long as it's not jQuery specific.