restructuredtext: TOC links broken when heading starts with "1."

[bgeron]

When a heading in a .rst file starts with "1. ", the links to it from the table of contents is broken.

Example: https://gist.github.com/bgeron/dffb1508aa6f383623de

[bgeron]

That is, in the HTML preview of the .rst file.

[gjtorikian]

I am 90% sure this is a dupe of #71 and should be fixed by #391.

[bgeron]

Yes, I agree. The added test case covers my problem.