Finally (mostly) fix window pulling-Now with added window pushing!

Created by: Exxion

That was actually surprisingly painless, considering how old and annoying this bug is. Windows can now be pulled in the direction they are facing. This was accomplished by making a special case for border objects in Adjacent(). (Don't worry, it's only one line.) Before checking if a border object is blocking the turf the targeted object is on, it now checks if the border object blocking the turf is the targeted object. This really shouldn't cause unintended behavior elsewhere, but I can't guarantee that it won't anyway due to the sheer quantity of old and/or weird code.

Fixes #3515 (closed).

Windows have a similar issue with being pushed in the direction they're facing. I'll look into that, too, but this PR doesn't fix it. Fixed it.

While testing this, I also noticed that windows can be pulled through anything except other windows in the opposite direction as they are facing, but this is unrelated to my change. I'll report that separately, though, as I can't fix it for reasons I will explain in the report.