exp/html: adjust beforeHTMLIM to match spec
exp/html: adjust beforeHTMLIM to match spec

Add case for doctype tokens (which are ignored).

This CL does not change the status of any tests.

R=golang-dev, nigeltao
CC=golang-dev
http://codereview.appspot.com/6061047

Committer: Nigel Tao <58ae08b3356928ff9c67562b4719487d54fe8348@golang.org>

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang