support "#'" syntax for function expressions

* module/language/elisp/lexer.scm (lex):
* module/language/elisp/parser.scm (get-expression): Support sharpsign
  single-quote syntax as an abbreviation for `function' expressions.

module/language/elisp/lexer.scm

@@ -314,10 +314,15 @@
                       (cons (integer->char (get-character port #t))
                             result-chars))))))
                (else (iterate (cons cur result-chars)))))))
-        ;; Circular markers (either reference or definition).
         ((#\#)
-         (let ((mark (get-circular-marker port)))
+         (let ((c (read-char port)))
-           (return (car mark) (cdr mark))))
+          (case c
+            ((#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9)
+             (unread-char c port)
+             (let ((mark (get-circular-marker port)))
+               (return (car mark) (cdr mark))))
+            ((#\')
+             (return 'function #f)))))
         ;; Parentheses and other special-meaning single characters.
         ((#\() (return 'paren-open #f))
         ((#\)) (return 'paren-close #f))

module/language/elisp/parser.scm

@@ -182,6 +182,8 @@
        (parse-error token "end of file during parsing"))
       ((integer float symbol character string)
        (return (cdr token)))
+      ((function)
+       (return `(function ,(get-expression lex))))
       ((quote backquote unquote unquote-splicing)
        (return (list (assq-ref quotation-symbols type)
                      (get-expression lex))))