[z-machine] Small contribution to the ZMachine specs

[Ben Collins-Sussman]

Pretty quiet list, eh?  Anyone awake?  :-)

There are really quite a number of confusions that Dave and I are
running into as we read the spec.  I'd love to keep sending patches to
re-word things, etc.

For example, I'm trying to understand how to do the lexical analysis
required by the 'read' opcode.  If I understand correctly, the user's
text is read into a text_buffer.  Is the user's text presumed to be
ascii data?  Unicode data?  Z-characters?