psql and pset without any arguments

Hi,

I was looking at psql 8.3 documention about \pset options and saw that
there was the following note :

    "Note: It is an error to call \pset without any arguments. In the
future this case might show the current status of all printing options."

I looked backward and forward to find that this note is present in all
versions since 7.1 up to 9.3, maybe it is time to add this little feature.

I've attached a patch to add the usage of the \pset command without any
arguments to displays current status of all printing options instead of
the error message. Here is a sample output:

        (postgres@[local]:5494) [postgres] > \pset
        Output format is aligned.
        Border style is 2.
        Expanded display is used automatically.
        Null display is "NULL".
        Field separator is "|".
        Tuples only is off.
        Title is unset.
        Table attributes unset.
        Line style is unicode.
        Pager is used for long output.
        Record separator is <newline>.
        (postgres@[local]:5494) [postgres] >

To avoid redundant code I've added a new method printPsetInfo() so that
do_pset() and exec_command() will used the same output message, they are
all in src/bin/psql/command.c. For example:

        (postgres@[local]:5494) [postgres] > \pset null 'NULL'
        Null display is "NULL".
        (postgres@[local]:5494) [postgres] >

The patch print all variables information from struct printTableOpt when
\pset is given without any arguments and also update documentation.

Let me know if there's any additional work to do on this basic patch or
something that I've omitted.

Best regards,

--
Gilles Darold
http://dalibo.com - http://dalibo.org