Make documentation of -W options more accurate and uniform.

contrib/vacuumlo/vacuumlo.c

doc/src/sgml/ref/clusterdb.sgml

doc/src/sgml/ref/createdb.sgml

doc/src/sgml/ref/createlang.sgml

doc/src/sgml/ref/createuser.sgml

doc/src/sgml/ref/dropdb.sgml

doc/src/sgml/ref/droplang.sgml

doc/src/sgml/ref/dropuser.sgml

doc/src/sgml/ref/pg_dump.sgml

doc/src/sgml/ref/pg_dumpall.sgml

doc/src/sgml/ref/pg_restore.sgml

doc/src/sgml/ref/psql-ref.sgml

doc/src/sgml/ref/reindexdb.sgml

doc/src/sgml/ref/vacuumdb.sgml

doc/src/sgml/vacuumlo.sgml

src/bin/psql/help.c

src/bin/scripts/clusterdb.c

src/bin/scripts/createdb.c

src/bin/scripts/createlang.c

src/bin/scripts/createuser.c