Added missing keywords for MySQL dialect

Added missing keywords for MySQL dialect

Fixes: #5696
Add missing MySQL keywords.

### Description
Adds some missing keywords from the MySQL dialect. While it's hard to describe this as a documentation/typographical fix, there are no current test for presence of the correct keywords, nor a realistic way to implement them those tests.

### Checklist
This pull request is:

- [x] A documentation / typographical error fix
	- Good to go, no issue or tests are needed
- [ ] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [ ] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

Closes: #5567
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5567
Pull-request-sha: db76e7f9d3a903cb4acf0309d57a14fe69948a0f

Change-Id: Ieaef45d0214fc9052a36924bfee38df9a27f7040