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.
@garoevans the two methods you modified is public API! This means it can be used in any context and is not only trigger by `getCreateTableSQL()`.
Creating indexes and unique constraints is supported by all of our platforms AFAIK. So putting the tests into `AbstractPlatformTestCase` makes perfect sense.