Internal representation of backquotes

[greek@DEC-HUDSON]

We would have to be very careful if we wanted to specify how backquotes
et al are represented when read in.  In PSL, you have an explicit
form for backquote et al, but in VAX LISP the reader converts the
backquotes into the actual LISP code needed to build the backquoted
lists.  So we lose all knowledge that a backquote was ever involved
(unless, of course, you turn on the magic variable that causes
us to remember).

I think we need to allow maximum flexibility in generating efficient
code for backquotes.

- Paul