Implement Date.Prototype.{getHours,getMinutes,getSeconds}.

Many tests (at least in the first ones of test262) were failing just because `Date.Prototype.getHours` and `Date.Prototype.getMinutes` were not implemented, so I implemented them.
I also implemented `getSeconds`.

I hope my implementation is ok. I tried to follow the standard and what you already implemented, but you probably should double-check this work.