HTML parser doesn't handle downlevel-revealed conditional comments

[davehunt]

I found that if a site is using downlevel-revealed conditional comments, the HTML parser aborts without any error. This truncates the number of links checked to those gathered before the comment is encountered, potentially leading to false confidence.

[dpalic]

Thank you for the issue report. Sadly this project is dead, and a new team is around with https://github.com/linkcheck/linkchecker for more details please see: #708 Also please close this issue and report it freshly on the new repo https://github.com/linkcheck/linkchecker/issues if your issue still persists