[patch] Fix bug: Articles not displayed in slrn after fetchnews run

Hi,

I am using leafnode+ 2.15 (run from inetd) and slrn 0.9.7.4 on FreeBSD
4.8-STABLE. This combination works very well most of the time, but every
now and then, slrn won't display new articles, that were fetched by fetchnews
before:

I see the number of new articles in slrn's overview screen, but when I
enter that group, all of the sudden none of the articles is available.

I was able to track the reason for this misbehaviour down:

slrn does an XOVER for that group say XOVER a-b. When leafnode+
processes that request, the following lines  in nntpd.c sometimes
decrease b (doxover(), line 886):

    if (xovergroup != group && !getxover()) {
        printf("224 Overview information not available\r\n.\r\n");
        return;
    }

    if (b == 0)
        b = xlast;

    if (a > xlast)
        b = xlast;
    if (b > xlast)
        b = xlast;
    if (a < xfirst)
        a = xfirst;