We now fire "pageshow" events at the appropriate time during document
loading (done by the parser.)
Note that there are no corresponding "pagehide" events yet.
This will be used to determine whether "pageshow" and "pagehide" events
are appropriate. We won't actually make use of it until we implement
more of history traversal and document unloading.
The only difference from what we were already doing is that setting the
same ready state twice no longer fires a "readystatechange" event.
I don't think that could happen in practice though.
We will now spin in "the end" until there are no more "things delaying
the load event". Of course, nothing actually uses this yet, and there
are a lot of things that need to.
