Update index name quoting in MySQL table creation

When creating a table that includes an index named with a reserved keyword the index name isn't quoted. When creating the index specifically the name is quote. This bring the table generation SQL inline with the index generation.
https://github.com/doctrine/dbal/pull/730#issuecomment-64934996 mentioned that MySQL is the only engine that creates engines along with a table create statement. I'm not sure the test would be relevant for other engines?

I did have the test higher up the abstraction at one point but it didn't seem right?