bug#19925: 25.0.50; mouseover menu items takes up to 30sec to show the proper tooltip or message

[Drew Adams <drew.adams@oracle.com>]

Moving the mouse over menu items, a user should see the associated
:help pretty much immediately - at most after a delay of a second or
two.

Instead, sometimes the help text is shown immediately, sometimes it is
shown only after, say, 30 seconds, and sometimes after any number of
seconds less than, say, 30.  I'm not sure, but I think the problem might
be somewhat more pronounced for items on a submenu or a subsubmenu.

The same problem occurs, regardless of whether tooltip mode is on.  That
is, it happens whether the mouseover text is shown in a tooltip or in
the echo area.

This bug renders mouseover help on menu items useless, and it makes
Emacs look pretty bad.

Worse: because the help text for a previously mouseovered menu item
remains displayed, a user can read it mistakenly as the help for the
item the mouse is currently over.  That is, the text is not removed when
you move mouse away from a given item, just as it is not updated when
you move mouse to another item.  The help display is, well, the
opposite of helpful.

In GNU Emacs 25.0.50.1 (i686-pc-mingw32)
 of 2014-10-20 on LEG570
Bzr revision: 118168 rgm@gnu.org-20141020195941-icp42t8ttcnud09g
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking=yes,glyphs CPPFLAGS=-DGLYPH_DEBUG=1'