Extra newlines added even if PQerrorMessage

Hi all,

2f52518 has removed a couple of extra newlines not needed as
PQerrorMessage is used, but some places have been missed:
- testlo64.c
- testlo.c
- findoidjoins.c
Those are not really critical, still I think that it would be good
practice to be consistent.

pgbench uses at one place CommandFailed() which appends automatically a
newline for the message passed by the caller, and calls one
PQerrorMessage. Perhaps CommandFailed()'s callers should just define a
newline in the message? Or it could be better to have a version of
pchomp for frontends?

Thanks,
--
Michael