ref. #2485

The `SystemCallError#to_s` method also needed to be modified, but since it has no functional difference from the `Exception#to_s` method, it will be removed.

Check the type of the keyword rest argument

If a non-hash object is passed in `OP_SEND` and `OP_SUPER`, an error should occur.

```ruby
kwd = "string"
p(**kwd)  #  => expect raised TypeError
```

`(irep->pool[b].tt & IREP_TT_NFLAG) == 0` is always true ensured by
the assertion.

Updated mruby-errno/README.md to pass the lint checks.

build(deps): bump github/super-linter from 4.8.6 to 4.8.7

Bumps [github/super-linter](https://github.com/github/super-linter) from 4.8.6 to 4.8.7.
- [Release notes](https://github.com/github/super-linter/releases)
- [Changelog](https://github.com/github/super-linter/blob/main/docs/release-process.md)
- [Commits](https://github.com/github/super-linter/compare/v4.8.6...v4.8.7)

---
updated-dependencies:
- dependency-name: github/super-linter
  dependency-type: direct:production
  update-type: version-update:semver-patch
...
Signed-off-by: dependabot[bot] <support@github.com>

build(deps): bump github/super-linter from 4.8.5 to 4.8.6

Bumps [github/super-linter](https://github.com/github/super-linter) from 4.8.5 to 4.8.6.
- [Release notes](https://github.com/github/super-linter/releases)
- [Changelog](https://github.com/github/super-linter/blob/main/docs/release-process.md)
- [Commits](https://github.com/github/super-linter/compare/v4.8.5...v4.8.6)

---
updated-dependencies:
- dependency-name: github/super-linter
  dependency-type: direct:production
  update-type: version-update:semver-patch
...
Signed-off-by: dependabot[bot] <support@github.com>

Add unlisted errno constants found in macOS and FreeBSD.
If you see unlisted errno, please report.

To reduce memory consumption by avoiding allocating Ruby objects.

Remove no longer used arguments from the functions.