Bugs in handling of Alt-key on w32

[Lennart Borgman <lennart.borgman.073@student.lu.se>]

I have been trying to get the Alt-key to work for accessing the menus 
(which is the normal use of it on w32). I think I found a couple of bugs:

On w32 start by setting

  (setq w32-pass-alt-to-system t)
  (setq w32-alt-is-meta nil)

Then try typing for example Alt, f. You can do that in two ways normally 
on w32:

    1) Either hold down Alt and then press f,
    2) or press and release Alt and then f.

Both these would open the File menu on a w32 app. In Emacs the first 
gives the message "A-f is undefined". The second alternative can give 
different results in Emacs depending on the time between typing Alt and 
f. Three things can happen as it works now (at least on a rather slow 
pc, 700MHz):

    a) the message "A-f is undefined"  --- when typing fast
    b) f is inserted in the buffer    --- typing a bit slower
    c) the File menu is opened   --- typing even slower

If StickyKeys (an accessibility option on w32, good to prevent hand 
damage too) are used another problem shows up too. You have to type Alt 
two times. (And I did not test carefully what can happen here).

I can not say I understand the code, but it seems to me that something 
is wrong in the handling of the Emacs specific messages queues on w32.

(I have told parts of this before, if someone remembers it.)