I don't see any sane reason for some of those to be PGDLLIMPORT but not others. In particular it's pretty silly for IsBackgroundWorker not to be PGDLLIMPORT.
Too trivial to be worth making an actual patch, it'd be more work to apply it than edit directly. -- Craig Ringer http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services