* Replace boilerplate for increment with a call to `increment`

from new tooling. Found cases to replace using `ripgrep`[1]:
```
$ rg '\(\*\w+\)\s*\+\+' -l | grep tools | grep -v old
```

[1]: https://github.com/BurntSushi/ripgrep

* Replace boilerplate for bigger than 1 increments with the new
`increment` call

from new tooling. Found cases to replace using `ripgrep`[1]:
```
$ rg '\(\*\w+\)\s*\+=' -l | grep tools | grep -v old
```

[1]: https://github.com/BurntSushi/ripgrep

* Update examples indicating the alternative increment call for hash tables