CLN: Add missing types to tslibs/conversion.pyx
Again just variables that were not typed, and removing some unused variables.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23984?src=pr&el=h1) Report
> Merging [#23984](https://codecov.io/gh/pandas-dev/pandas/pull/23984?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/982c169a286d436481364d2a6c27b355a83472b5?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/23984/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23984?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #23984   +/-   ##
=======================================
  Coverage   92.31%   92.31%           
=======================================
  Files         161      161           
  Lines       51513    51513           
=======================================
  Hits        47554    47554           
  Misses       3959     3959
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.71% <ø> (ø)` | :arrow_up: |
| #single | `42.42% <ø> (ø)` | :arrow_up: |


------

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> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23984?src=pr&el=footer). Last update [982c169...d97cecb](https://codecov.io/gh/pandas-dev/pandas/pull/23984?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks i think this broke 32 bit

https://travis-ci.org/MacPython/pandas-wheels/jobs/461611536
cc @jbrockmendel 
cc @jschendel  I am guessing it was one of these declarations, but it's not obvious to me which one it was since they are all derived from each other:

https://github.com/pandas-dev/pandas/pull/23984/files#diff-66d289312fd0b02e7721bf45fb281797R891 