[Simh] PDP-15/76

[Andrew Warkentin]

I believe XVM/RSX supports it as well (although it is dependent on
XVM/DOS for booting so the UC15 simulation will have to be working
with XVM/DOS first). Not sure whether the distribution that's
available includes enough to support it (since SIMH didn't support it
I didn't look at that part too closely when I was figuring out how to
install RSX). However, I would be surprised if it requires anything
that's not included in either the RSX or DOS kits.