This patch implements $subject only when ANALYZE and VERBOSE are on. I made it that way because for years nobody seemed interested in this info (at least no one did it) so i decided that maybe is to much information for most people (actually btree indexes are normally very fast).
But because we have GiST and GIN this became an interested piece of data (there are other cases even when using btree).
Current patch doesn't have docs yet i will add them soon.
