Fix pg_restore to complain if any arguments remain after parsing the switches

Fix pg_restore to complain if any arguments remain after parsing the switches
and input file name, per bug #5617 from Leo Shklovskii.  Rearrange the
corresponding code in pg_dump and pg_dumpall so that all three programs
handle this in a consistent, straightforward fashion.

Back-patch to 9.0, but no further.  Although this is certainly a bug, it's
possible that people have scripts that will be broken by the added error
check, so it seems better not to change the behavior in stable branches.