Docs incorrectly claiming equivalence between show and pg_settings

Hi!

http://www.postgresql.org/docs/devel/static/sql-show.html claims:
"Also, the pg_settings system view produces the same information."

This is not entirely correct. On IRC I was told, that the view only contains
settings set from C, not user defined settings defined by the SET command:

timemngt=# set my.test = 'test';
SET
timemngt=# show my.test;
┌─────────┐
│ my.test │
├─────────┤
│ test │
└─────────┘
(1 row)

timemngt=# select * from pg_settings where name = 'my.test';
timemngt=#

Including this rather obscure bit of information might help another user down
the road.

Thanks,
Stefan Seifert