pg_dump and pg_restore were stripping quotes and downcasing some but

pg_dump and pg_restore were stripping quotes and downcasing some but
not all SQL identifiers taken from command line arguments.  We decided
years ago that that was a bad idea: identifiers taken from the command
line should be treated as literally correct.  Remove the inconsistent
code that has crept in recently.  Also fix pg_dump so that the combination
of --schema and --table does what you'd expect, namely dump exactly one
table from exactly one schema.  Per gripe from Deepak Bhole of Red Hat.