bug#50067: Context menus

[Juri Linkov]

After typing 'C-h k', clicking mouse-3 on a function name,
then selecting e.g. "Describe Function", the Help buffer says

  <down-mouse-3> <describe-symbol> at that spot is undefined

This can be fixed by this patch:

diff --git a/lisp/help.el b/lisp/help.el
index 8f77167040..b794751eca 100644
--- a/lisp/help.el
+++ b/lisp/help.el
@@ -695,7 +695,7 @@ help--analyze-key
         (mouse-msg (if (or (memq 'click modifiers) (memq 'down modifiers)
                            (memq 'drag modifiers))
                         " at that spot" ""))
-        (defn (key-binding key t)))
+        (defn (save-excursion (mouse-set-point event) (key-binding key t))))
     ;; Handle the case where we faked an entry in "Select and Paste" menu.
     (when (and (eq defn nil)
               (stringp (aref key (1- (length key))))
--