9.3 release notes:  adjustments

Fixes from Peter Geoghegan, Ian Lawrence Barwick, Marti Raudsepp
docs:  fix log_line_prefix session id docs

Backpatch to 9.2.

Report from Ian Lawrence Barwick
9.3 docs:  wording fixes

From Erik Rijkers
docs:  log_line_prefix session id fix

Restore 4-byte designation for docs.  Fix 9.3 doc query to properly pad
to four digits.

Backpatch to all active branches

Per suggestions from Ian Lawrence Barwick
docs:  Improve log_line_prefix session_id query
Improve behavior of \watch with non-tuple-returning commands.

Print the command tag if we get PGRES_COMMAND_OK, and throw an error for
other cases.  Per gripe from Michael Paquier.

In passing, add an fflush(), just to be real sure the output appears
before we sleep.