Rendering in close corners

[katexochen]

Sometimes corners that are close to each other cannot be rendered as desired:

The following is kind of expected:

+----------+
|  PCRn    |
+----------+
+----------+
| Nonce    |
+----------+

It would be great if using other corners would not connect the two boxes:

+----------+
|  PCRn    |
'----------'
.----------.
| Nonce    |
+----------+

but it currently renders the same as with +

[dmullis]

See fix referenced above.

[dmullis]

Fix mentioned above will be preserved in https://github.com/dmullis/goat/tree/github-test rather than in the main branch of my fork.