DEC VT20 boot device

[Noel Chiappa]

    > From: Paul Birkel

    > Apparently the VT20 used the M792-YK as its bootstrap; the Field Guide
    > is silent regarding the boot device and M792 documentation stops
    > earlier in the series of variants.

An M792-YK recently sold on eBait; I didn't get it, but I did manage to get
the seller to put up good photos of the board, so was able to dump the
contents.

I didn't fully disassamble the program, but it was clearly something serial
line related. With the VT20 info, it's now clear what it was for. It should be
pretty easy to fully disassamble, and work out the protocol.

I have the dump of the contents if anyone has a use for them. 

	Noel