Yields should collapse by default
Many users like to use "yield" in their page handlers, but aren't prepared for the side-effects of this choice when using HTTP/1.1. Even those developers who need the streaming functionality report that they need it infrequently. Rather than ask people to use "return", we should instead collapse generator-bodies by default. A config entry, "collapseYields" (True by default), should be introduced; setting it to False would enable streamed yields for that path. Therefore, in order to enable streaming yields, you'd have to have HTTP/1.1 on both the client and server sides AND set this value; I don't think that's too much to ask given how uncommon the need is.
My only remaining question is whether this could be sneaked into 2.1 or not...I'd like it to be.