pgsql: Disable pg_standby -l option because the backend doesn't expect

Log Message:
-----------
Disable pg_standby -l option because the backend doesn't expect the recovered
file to be a symlink. We tried to fix this issue with an earlier server-side
patch, but it didn't fix the whole issue.

The same bug is present in older releases as well, but the 8.4 train is
about to leave the station, and I'm not sure if have consensus on whether
we can remove the -l option in back-branches or do we need to attempt a
server-side fix to make symlinking safe.

Patch by Simon Riggs, per discussion on bug identified by Fujii Masao.

Modified Files:
--------------
pgsql/contrib/pg_standby:
pg_standby.c (r1.24 -> r1.25)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_standby/pg_standby.c?r1=1.24&r2=1.25)
pgsql/doc/src/sgml:
pgstandby.sgml (r2.9 -> r2.10)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pgstandby.sgml?r1=2.9&r2=2.10)