TST: Skip 32bit failing IntervalTree tests
xref #23440, https://github.com/pandas-dev/pandas/pull/23353#issuecomment-434642190

Note that we've been skipping tests due to this issue for some time now, it just wasn't formally documented as an issue:

https://github.com/pandas-dev/pandas/blob/9019582c45d17035098941a666a8b6072c13a357/pandas/tests/indexes/interval/test_interval_tree.py#L88-L91

I recently added some new tests that hit this same issue but were not skipped and are now causing the pandas-wheels nightly builds to fail.  This PR causes those tests to be skipped on 32bit, and modifies the existing skipped test to skip at the parameter level instead of globally skipping the test (one of the previously skipped parametrized values should be valid on 32bit).



Hello @jschendel! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/tests/indexes/interval/test_interval_tree.py`](https://github.com/jschendel/pandas/blob/585127d20311630e2ca0c81a38f3e6988c621b95/pandas/tests/indexes/interval/test_interval_tree.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23442?src=pr&el=h1) Report
> Merging [#23442](https://codecov.io/gh/pandas-dev/pandas/pull/23442?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9019582c45d17035098941a666a8b6072c13a357?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23442/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23442?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #23442   +/-   ##
=======================================
  Coverage   92.21%   92.21%           
=======================================
  Files         161      161           
  Lines       51187    51187           
=======================================
  Hits        47202    47202           
  Misses       3985     3985
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.64% <ø> (ø)` | :arrow_up: |
| #single | `42.21% <ø> (ø)` | :arrow_up: |


------

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 thanks! https://travis-ci.org/MacPython/pandas-wheels/jobs/449669142

hmm this is now failing for a different reason

.get_indexer should be returning platform int - but it’s not ? (maybe just this case) Hi,

I get failures on my 32bit installation when leaf_size=10000.