strerror (was Re: Various problem with xconq)

[Jim Kingdon]

>I also found this patch in the Debian bug tracking system:
>http://bugs.debian.org/107313

Thanks; I have checked in a slightly modified version of that patch
(in addition to some whitespace cleanups, I just assumed that errno.h
declares errno - this is required by C89 which xconq requires anyway).

On my Red Hat Linux system using the tcltk user interface, it didn't
seem like the SelFile.c code was actually being called (but maybe I
just didn't know where to call it from).  So this might be a moot
point.  But worth fixing, anyway.