org-macro--set-templates: Prevent code evaluation

* lisp/org-macro.el (org-macro--set-templates): Get rid of any
risk to evaluate code when `org-macro--set-templates' is called as a
part of major mode initialization.  This way, no code evaluation is
ever triggered when user merely opens the file or when
`mm-display-org-inline' invokes Org major mode to fontify mime part
preview in email messages.

lisp/org-macro.el

@@ -109,6 +109,13 @@ previous one, unless VALUE is nil.  Return the updated list."
   (let ((new-templates nil))
     (pcase-dolist (`(,name . ,value) templates)
       (let ((old-definition (assoc name new-templates)))
+        ;; This code can be evaluated unconditionally, as a part of
+        ;; loading Org mode.  We *must not* evaluate any code present
+        ;; inside the Org buffer while loading.  Org buffers may come
+        ;; from various sources, like received email messages from
+        ;; potentially malicious senders.  Org mode might be used to
+        ;; preview such messages and no code evaluation from inside the
+        ;; received Org text should ever happen without user consent.
         (when (and (stringp value) (string-match-p "\\`(eval\\>" value))
           ;; Pre-process the evaluation form for faster macro expansion.
           (let* ((args (org-macro--makeargs value))
@@ -121,7 +128,7 @@ previous one, unless VALUE is nil.  Return the updated list."
 		      (cadr (read value))
 		    (error
                      (user-error "Invalid definition for macro %S" name)))))
-	    (setq value (eval (macroexpand-all `(lambda ,args ,body)) t))))
+	    (setq value `(lambda ,args ,body))))
         (cond ((and value old-definition) (setcdr old-definition value))
 	      (old-definition)
 	      (t (push (cons name (or value "")) new-templates)))))