review: psql and pset without any arguments

* we would this feature - it is consistent with \set and it gives a fast resume about psql printer settings

Issues:

1) it doesn't show linestyle when is default

I looked there and it is probably a small different issue - this value is initialized as NULL as default. But I dislike a empty output in this case:

    else if (strcmp(param, "linestyle") == 0)
    {
        if (!popt->topt.line_style)
            ;
        else
            printf(_("Line style is %s.\n"),
                   get_line_style(&popt->topt)->name);
    }

I propose a verbose result instead nothing:

    else if (strcmp(param, "linestyle") == 0)
    {
        if (!popt->topt.line_style)

           printf(_("Line style is unset.\n")) ;

        else
            printf(_("Line style is %s.\n"),
                   get_line_style(&popt->topt)->name);
    }