pgsql: Fix erroneous implementation of -s in postmaster.c (the switch

Log Message:
-----------
Fix erroneous implementation of -s in postmaster.c (the switch doesn't take
an optarg). Add some comments noting that code in three different files has
to be kept in sync. Fix erroneous description of -S switch (it sets work_mem
not silent_mode), and do some light copy-editing elsewhere in postgres-ref.

Modified Files:
--------------
pgsql/doc/src/sgml/ref:
postgres-ref.sgml (r1.47 -> r1.48)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/postgres-ref.sgml.diff?r1=1.47&r2=1.48)
pgsql/src/backend/main:
main.c (r1.105 -> r1.106)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/main/main.c.diff?r1=1.105&r2=1.106)
pgsql/src/backend/postmaster:
postmaster.c (r1.505 -> r1.506)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c.diff?r1=1.505&r2=1.506)
pgsql/src/backend/tcop:
postgres.c (r1.519 -> r1.520)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/postgres.c.diff?r1=1.519&r2=1.520)