TST: A test to cover fault in issue #5291
The mentioned issue faulted under similar conditions as issue #13703, and was also fixed by PR #13788. This PR just adds a test to replicate the fault, as discussed in the issue's thread.
- [x] closes #5291
- [x] tests added / passed
- [x] passes `git diff upstream/master | flake8 --diff`
- [x] whatsnew entry

This PR also corrects accidental use of **float("nan")** instead of **np.nan** in [`test_parse_trim_buffers`](https://github.com/pydata/pandas/blob/master/pandas/io/tests/parser/c_parser_only.py#L442).
