Hyphens and underscores in mysql.cnf

According to [this bug](https://bugs.mysql.com/bug.php?id=55288) `_`and `-` may both be used in mysql / mariadb configuration options inside the `mysql.cnf` file.

E.g.
```
[mariadb]
log-bin                         # enable binary logging
```
and 
```
[mariadb]
log_bin                         # enable binary logging
```
are both ok!

For googling and searching inside pages the `_` variant usually works better.

alexanderpresber
November 3, 2022