[HACKERS] Clarifying "server starting" messaging in pg_ctl start without --wait

I had an issue earlier where I was trying to upgrade my postgres database to a new major version and incidentally a new pg_catalog version, and therefore the new code could no longer run the existing data directory without pg_upgrade or pg_dump (I ended up needing pg_dump).  Initially I was very confused because I tried running "pg_ctl -D datadir -l logfile start" like normal, and it just said "server starting", yet the server was not starting.  It took me a while to realize that I needed to use the "--wait" / "-w" option to actually wait and test whether the server was really starting, at which point it told me there was a problem and to check the log.