pgsql: Add \conninfo command to psql, to show current connection info.

[rhaas(at)postgresql(dot)org (Robert Haas)]

Log Message:
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Add \conninfo command to psql, to show current connection info.

David Christensen. Reviewed by Steve Singer.  Some further changes by me.

Modified Files:
--------------
    pgsql/doc/src/sgml/ref:
        psql-ref.sgml (r1.245 -> r1.246)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/psql-ref.sgml?r1=1.245&r2=1.246)
    pgsql/src/bin/psql:
        command.c (r1.221 -> r1.222)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/command.c?r1=1.221&r2=1.222)
        help.c (r1.159 -> r1.160)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/help.c?r1=1.159&r2=1.160)
        tab-complete.c (r1.200 -> r1.201)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/tab-complete.c?r1=1.200&r2=1.201)