bug#55203: 29.0.50; MSW menu bar help text doesn't show when blink-cursor-mode is off

[Eli Zaretskii]

> Date: Sun, 01 May 2022 11:00:11 +0800
> From:  Po Lu via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> 
> Move the mouse over any menu bar item that normally shows a tooltip.
> That tooltip will not be displayed if `blink-cursor-mode' is turned off.

This is a well-known problem.  It is caused by the implementation of
Emacs menus on MS-Windows: we start a separate message loop for
handling the menu events, and this suspends the main event loop.  When
blink-cursor-mode is ON, the timer causes the main event loop to turn
a notch, and then Emacs produces the help-echo for the menu item; but
without cursor blinking and no other sources of async input events,
that doesn't happen.

Patches to fix that are welcome.