Also fix #127 with addinfourl

[SimonSapin]

Reported on IRC by @mattaustin: http://krijnhoetmer.nl/irc-logs/whatwg/20131227#l-188

[hoppipolla-critic-bot]

Critic review: https://critic.hoppipolla.co.uk/r/490

This is an external review system which you may optionally use for the code review of your pull request.

In order to help critic track your changes, please do not make in-place history rewrites (e.g. via git rebase -i or git commit --amend) when updating this pull request.

[mattaustin]

I tested this in my app which used FancyURLOpener().open(), and returned a urllib.response.addinfourl instance. using Python 3.3 (Python 2.7 and 3.2 were unaffected), before the patch, the parser returned an empty html document. Afterwards it returned the expected content. Thanks @SimonSapin

[gsnedders]

As I said on IRC to @SimonSapin: Can we change this to just pass a firstChunk into HTMLUnicodeInputStream and HTMLBinaryInputStream, so we can work around all 20007 issues all at one? It's ugly, but it stops endless isinstance checks for this.