mouse-4/mouse-5 loses click modifiers

[Juri Linkov]

A recipe to reproduce this bug:

1. Run emacs -Q

2. M-: (get 'S-mouse-5 'event-symbol-elements) RET
(mouse-5 shift click)

3. Press the Shift key, and scroll the mouse wheel up/down.

4. M-: (get 'S-mouse-5 'event-symbol-elements) RET
(mouse-5 shift)

A list of modifiers now misses the `click' element that was here
initially.  As a result, mouse-avoidance-ignore-p fails to ignore
mouse wheel's scrolling events because it checks event-modifiers
for the `click' modifier.  The same bug applies to other modifiers
defined in `mouse-wheel-scroll-amount'.

GNU Emacs 22.1.50 (i686-pc-linux-gnu, GTK+ Version 2.10.12)

-- 
Juri Linkov
http://www.jurta.org/emacs/