CLN: Removed second version of xstrtod in parser_helper.h
- [x] closes #19361
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=h1) Report
> Merging [#25925](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1d4c89f4d747854def6c32733383b4afa250165d?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25925/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25925      +/-   ##
==========================================
- Coverage    91.8%   91.79%   -0.01%     
==========================================
  Files         174      174              
  Lines       52536    52536              
==========================================
- Hits        48231    48226       -5     
- Misses       4305     4310       +5
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.35% <ø> (ø)` | :arrow_up: |
| #single | `41.88% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/25925/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `75% <0%> (-12.5%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/25925/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.79% <0%> (-0.12%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25925/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `90.63% <0%> (-0.11%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=footer). Last update [1d4c89f...d7c6ffa](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=h1) Report
> Merging [#25925](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/f0ba498f71a9aed5b9cfda6ad6099fe9e7292cda?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25925/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25925      +/-   ##
==========================================
- Coverage   91.81%    91.8%   -0.01%     
==========================================
  Files         175      175              
  Lines       52578    52578              
==========================================
- Hits        48273    48269       -4     
- Misses       4305     4309       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.36% <ø> (ø)` | :arrow_up: |
| #single | `41.9% <ø> (-0.08%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/25925/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `75% <0%> (-12.5%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/25925/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.79% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=footer). Last update [f0ba498...7d56a15](https://codecov.io/gh/pandas-dev/pandas/pull/25925?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @anmyachev : Thanks for the PR!

Can you run `asv` benchmarks to see if performance is impacted with this de-duplication? AFAICT this looks fine, but I'm going to kick the review over to @chris-b1 who is better-versed in this area. @jbrockmendel: Sounds good.  Was just pinging for the modified dependency linking (given your thoughts interest in reorganizing internal dependencies to make it more DAG) @gfyoung after this run:
`asv continuous -f 1.01 origin/master HEAD -e -b inference.MaybeConvertNumeric ` 
result: `BENCHMARKS NOT SIGNIFICANTLY CHANGED.`
Same result for run `asv continuous -f 1.01 origin/master HEAD -e -b io.csv`
- First run check perf of xstrtod with `maybe_int != NULL` 
- Second run check perf of xstrtod with `maybe_int == NULL` @chris-b1 any comments here thanks @anmyachev 