Simon Burge found and fixed a bug in sysinst on pmaxs.

The menu to unpack distribution tar files is too big for an 80x24
display, and sysinst would coredump when trying to display it.  This
does not affect installs using the `rcons' graphics console or using
large terminals (e.g., 40-line xterms) as console terminals.

I've applied Simon's fix to my own tree and I'm rebuilding the
diskimage.gz and diskimage.tar.gz files.

If you want to install from an 80x24 console device, you should wait
till the updated binaries are available.

A big thanks to Simon for finding and fixing this; I couldn't
reproduce it, because I was using large displays.