Convert rtguts.mss to texinfo
Since we have "rtguts.mss" that describes internal design for the RT PC, we should convert it to texinfo. This is mostly for historical reference since we do currently link to the scanned pdf.
It would be nice to have an HTML version of the doc.
Shouldn't be too hard since it's in Scribe format and is only 182 KB long, about the same size as the Hemlock Command Implementor's Manual.