There have been many discussions about adding hints to Postgres over the years. All have been firmly rejected by the Postgres developers, with well-argued reasons. Search the archives to learn more about this topic.
On the other hand, Postgres does have hints. They're just called settings. You can disable certain types of joins with SET commands. On top of that, there are "fences" that the optimizer can't cross that you can use to force the optimizer to consider certain sub-queries separately (e.g. "offset 0" on a subquery).
Craig