[tz] Spain may change time

[Paul Eggert]

Thanks, I had overlooked those '25h's. I'm afraid I'm not seeing how to 
summarize all this in the 'europe' file, though. Perhaps something like 
this?

Officially, in the 1918 and 1919 fallback transitions the clock for the 
long day kept going after 24:00, reaching 24:59 the previous day before 
falling back an hour to 00:00 the next day. As this behavior is not 
representable in this database, it is modeled instead as the clock 
reaching 00:59 the next day before falling back to 00:00.