different approach to overriding SQL in annotations

[gavinking]

Introduces the @ForDialect annotation, which is really a perfectly elegant thing if you're careful not to look at its implementation.

This approach has the advantage that it doesn't impact the existing annotations at all: it's completely self-contained.

See #4528.

[gavinking]

Note, with this new annotation, you can write things like:

@Entity(name = "Person")
@Check(constraints = "code > 0")
@ForDialect(dialect = H2Dialect.class, 
            check = @Check(constraints = "sign(code) = 1"))
public static class Person { ... }

[gavinking]

Does anyone know what's up with MySQL and Maria? Why they keep timing out?

[beikov]

Can you rebase? I fixed the hanging yesterday evening.

[gavinking]

I fixed the hanging yesterday evening.

Thanks, that worked.

[gavinking]

I have merged this. It's marked @Incubating, and it's very under-tested, since some of this is quite hard to write tests for. Hell, I noticed that we have no tests for @Check at all. Let's see if people find it useful.