[plt-scheme] getting sysadmins to install DrScheme

A mea culpa note from me. My problems with the slowly-loading and
eventually-failing version of DrScheme (Unix/X11) installed by my
sysadmins was due to obsolete settings of my PLTHOME and PLTCOLLECTS
variables, which were pointing at 206.1 while I was trying to run
207. I still have the problem that when running setup-plt on both my local
copy of DrScheme and on the sysadmin-installed copy, it fails late in
the installation process while trying to compile .zos for the SSL
Driver (the sysadmin gets past that and bombs on Plot Library). I
still have no idea what this leaves undone, but at least DrScheme is
loading nicely now. Sorry to have bothered everyone. --PR