[tz] OpenJDK/CLDR/ICU/Joda issues with Ireland change

[Paul Eggert]

Meno Hochschild wrote:
> I would prefer not to have mixed signs within the same set of rules equally named.

Wouldn't that in some cases force rulesets to be split into multiply-named Rules 
merely to satisfy the restriction, thus complicating Zones that refer to the 
affected rulesets? That doesn't sound like a good restriction to add, at least 
from the tzcode/tzdata point of view.