pgsql: Improve documentation of psql's \q command.

Improve documentation of psql's \q command.

The documentation neglected to explain its behavior in a script file
(it only ends execution of the script, not psql as a whole), and failed
to mention the long form \quit either.

Branch
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REL9_0_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/606990dcf898243f635b421d5d99439cbbf8ddc2

Modified Files
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doc/src/sgml/ref/psql-ref.sgml |    3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)