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).

I think this PR and PR #13788 also close the issue #11793.
 ## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/13833?src=pr) is 85.25% (diff: 100%)

> Merging [#13833](https://codecov.io/gh/pydata/pandas/pull/13833?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will increase coverage by **0.01%**

``` diff
@@             master     #13833   diff @@
==========================================
  Files           140        140          
  Lines         50451      50455     +4   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          43003      43015    +12   
+ Misses         7448       7440     -8   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [b2a1445...4a74d50](https://codecov.io/gh/pydata/pandas/compare/b2a14459cf97af53ecc5edf51659ce3a9f1125b4...4a74d50c75cfb827f3c2b3b6d2605249dfe80c90?src=pr)
