Design big-endian uuo link execute caches.

Design big-endian uuo link execute caches.

The little-endian hack to overwrite the tag with instructions doesn't
work on big-endian because it's the datum, not the tag, that's at the
end of the word in the frame size.

There's no room for the instructions before anything here, so add
another word and move the frame size to the end.  Kinda wasteful --
for that matter, it's not clear why we need to have any instructions
here at all, when we could just have INVOCATION:UUO-LINK compile to
an IJUMP instruction itself.