BUG: use internal linkage (static variables) in move.c
move.c declared global variables without explicitly declaring them static, so
they had global visibility. This meant that if you linked against a shared
object that provided the same symbols, the wrong data would be read. In
particular: linking to libgtk, which provides the symbol 'methods', would cause
an import error of pandas.util._move.

- [x] closes #19706
- [ ] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24113?src=pr&el=h1) Report
> Merging [#24113](https://codecov.io/gh/pandas-dev/pandas/pull/24113?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9f2c7164ec581a484ee167c04478bf9e4f81426b?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/24113/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24113?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24113      +/-   ##
==========================================
- Coverage    92.2%    92.2%   -0.01%     
==========================================
  Files         162      162              
  Lines       51714    51714              
==========================================
- Hits        47682    47681       -1     
- Misses       4032     4033       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <ø> (ø)` | :arrow_up: |
| #single | `43.01% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24113?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/json/json.py](https://codecov.io/gh/pandas-dev/pandas/pull/24113/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2pzb24vanNvbi5weQ==) | `92.61% <0%> (-0.48%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24113/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.51% <0%> (+0.09%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24113?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/24113?src=pr&el=footer). Last update [9f2c716...c88d9ea](https://codecov.io/gh/pandas-dev/pandas/pull/24113?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/24113?src=pr&el=h1) Report
> Merging [#24113](https://codecov.io/gh/pandas-dev/pandas/pull/24113?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/b78aa8d8506ac119124619a9e03ff1482262e0cc?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/24113/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24113?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24113      +/-   ##
==========================================
- Coverage    92.2%    92.2%   -0.01%     
==========================================
  Files         162      162              
  Lines       51701    51701              
==========================================
- Hits        47672    47671       -1     
- Misses       4029     4030       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <ø> (ø)` | :arrow_up: |
| #single | `43.02% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24113?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/json/json.py](https://codecov.io/gh/pandas-dev/pandas/pull/24113/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2pzb24vanNvbi5weQ==) | `92.61% <0%> (-0.48%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24113/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.51% <0%> (+0.09%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24113?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/24113?src=pr&el=footer). Last update [b78aa8d...8b62a41](https://codecov.io/gh/pandas-dev/pandas/pull/24113?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 unclear how/if we want to test this case. Also, do you want a whatsnew for a (small) bugfix like this? thanks @llllllllll this looks fine. can you add a whatsnew note, ping on green. I moved the whatsnew entry to other and removed the link. Sorry about putting it in "categorical" before, I just searched for "bugs" quickly. Tests are now passing. cc @jreback  Thanks!