Link with names that clashed with properties inherited from the
Object prototype (such as "constructor") were not expanding. This fixes
this issue.
Before this change, markdown of this form...:
Link: [constructor][].
[constructor]: https://example.org/
...resulted in HTML output of this form:
<p>Link: [constructor][].</p>
With this change, it now renders as expected:
<p>Link: <a href="https://example.org/">constructor</a>.</p>
04e04b10d4