(Fcar, Fcdr): Add links to Elisp manual to the docstrings.

src/data.c

@@ -521,7 +521,10 @@ DEFUN ("floatp", Ffloatp, Sfloatp, 1, 1, 0,
 
 DEFUN ("car", Fcar, Scar, 1, 1, 0,
        doc: /* Return the car of LIST.  If arg is nil, return nil.
-Error if arg is not nil and not a cons cell.  See also `car-safe'.  */)
+Error if arg is not nil and not a cons cell.  See also `car-safe'.
+
+See Info node `(elisp)Cons Cells' for a discussion of basic Lisp
+concepts such as car, cdr, cons cell and list.  */)
      (list)
      register Lisp_Object list;
 {
@@ -549,7 +552,10 @@ DEFUN ("car-safe", Fcar_safe, Scar_safe, 1, 1, 0,
 
 DEFUN ("cdr", Fcdr, Scdr, 1, 1, 0,
        doc: /* Return the cdr of LIST.  If arg is nil, return nil.
-Error if arg is not nil and not a cons cell.  See also `cdr-safe'.  */)
+Error if arg is not nil and not a cons cell.  See also `cdr-safe'.
+
+See Info node `(elisp)Cons Cells' for a discussion of basic Lisp
+concepts such as cdr, car, cons cell and list.  */)
      (list)
      register Lisp_Object list;
 {