Confusing recovery message when target not hit

Hi all,

When recovery_target_time is set, but recovery finishes before it reaches
that time, it outputs "before 2000-01-01 00:00:00+00" to the .history
file. This is because it uses recoveryStopTime, which is initialised to 0,
but is never set, and is then passed to timestamptz_to_str, which gives it
this date output.

A similar problem exists for recovery_target_xid. When recovery finishes
before reaching the specified xid, it outputs "before transaction 0" to the
.history file, which is also confusing.

Could we produce something more meaningful? I've attached a patch which
changes it to say 'recovery reached consistency before recovery target time
of "<recovery_target_time>"' and 'recovery reached consistency before
recovery target xid of "<recovery_target_xid>"'.

It may be the wrong way of going about it, but you get the idea of what I'm
suggesting we output instead.

Thom