RSTS V10.1 patch

[Paul Koning]

I just added a patch to https://github.com/pkoning2/decstuff, in patches/shut.cmd, which cures a problem in RSTS V10.1 that seems to come and go with no clear pattern.  The failure is a crash, sometimes a halt, during system shutdown.  The cause was a write to the wrong location when removing the DCL runtime system, because of a register not being set before that action.

The patch can be installed with ONLPAT; it takes effect immediately (because it patches a non-resident overlay).

	paul