zlisp: add proper (point) and (mark) support.

* lib/zmacs/zlisp/buffer.zl (point): New function. Returns the
byte offset of point in the current buffer.
* lib/zmacs/zlisp/marker.zl (mark): New function. Returs the
byte offset of mark in the current buffer, if any.
* NEWS: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
zlisp: a fully functional reader and evaluator!

* lib/zile/zlisp.lua (parse): When pushing a quoted node onto
the AST, it goes at the front of the cons list!
* lib/zmacs/eval.lua (marshaller): Except for special forms, now
marked with "UNEVAL" in defsubr max parameter, evaluate each
parameter before calling the subr.
(eval_expression): Rewrite. Get values of variable symbols, call
function symbols at the head of a cons list, and handle `quote`
specially until special-forms support is complete.
* lib/zmacs/zlisp/variables.zl (set-variable): No need to tease
out the variable symbol from a quoted cons list any more.
* NEWS: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
zlisp: don't crash when passing non-strings to (message).

* lib/zmacs/zlisp/minibuf.zl (message): Coerce argument to a
string before echoing.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
zlisp: copy-region-as-kill now interprets parameters.

* lib/zmacs/zlisp/buffer.zl (point-min, point-max, buffer-size):
New lisp functions.
* lib/zmacs/zlisp/killring.zl (copy-region-as-kill): Interpret
arguments as describing region offsets.
* NEWS: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>