Correct broken entries for pg_proc OIDs 1364 (time(abstime))

and 1370 (timestamp(datetime)).  This does not force an initdb, exactly,
but you won't see the effects of the bug fix until you do one.
BTW, OID 1358 for timespan(time) is still broken:
select timespan('21:11:26'::time);
ERROR:  No such function 'time_timespan' with the specified attributes
But I couldn't figure out what it ought to be defined as, so I left it be.