bug#28732: flymake mouse-wheel portability fix

[Charles A. Roelli]

The flymake mode line mouse-wheel scroll thing needs the following fix
to be more portable.

This change also removes an extra newline at the end of the tooltip,
which doesn't have to be there as far as I can see.

diff --git a/lisp/progmodes/flymake.el b/lisp/progmodes/flymake.el
index 45f0adf..007de8f 100644
--- a/lisp/progmodes/flymake.el
+++ b/lisp/progmodes/flymake.el
@@ -951,11 +951,13 @@ flymake--mode-line-format
                      keymap
                      ,(let ((map (make-sparse-keymap))
                             (type type))
-                        (define-key map [mode-line mouse-4]
+                        (define-key map (vector 'mode-line
+                                                mouse-wheel-down-event)
                           (lambda (_event)
                             (interactive "e")
                             (flymake-goto-prev-error 1 (list type) t)))
-                        (define-key map [mode-line mouse-5]
+                        (define-key map (vector 'mode-line
+                                                mouse-wheel-up-event)
                           (lambda (_event)
                             (interactive "e")
                             (flymake-goto-next-error 1 (list type) t)))
@@ -967,7 +969,9 @@ flymake--mode-line-format
                                                   'face face)
                                       (propertize (format "%s" type)
                                                   'face face))
-                              "mouse-4/mouse-5: previous/next of this type\n"))
+                              (format "%s/%s: previous/next of this type"
+                                      mouse-wheel-down-event
+                                      mouse-wheel-up-event)))
            into forms
            finally return
            `((:propertize "[")