Support for TINYINT and MEDIUMINT

I know that TINYINT and MEDIUMINT are specific to mysql/mariadb that why I create this issue here.
Currently you can use both types but get the following warning

```
[WARN] Using unknown data type MEDIUMINT
```

Would it not be better to implement the specific types in the driver that can handle these?

I can create a PR for that, but you need to tell me how I should define the new data types, because currently they are defined in _db-migrate-shared_.

---
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