Request body: only read body in main request (ticket #330). Before 1.3.9 an attempt to read body in a subrequest only caused problems if body wasn't already read or discarded in a main request. Starting with 1.3.9 it might also cause problems if body was discarded by a main request before subrequest start. Fix is to just ignore attempts to read request body in a subrequest, which looks like right thing to do anyway.