bug#9874: Fixes for several integer overflow and width issues

[Paul Eggert]

Stefan OKed this patch so I installed this into the trunk
as bzr 108370 and am marking the bug as done.  The idea
is to give Dmitry a chance to rework his proposal for
immediate strings
<http://lists.gnu.org/archive/html/emacs-devel/2012-05/msg00435.html>
in the light of the usually-smaller data structures when
configured --with-wide-int on 32-bit hosts.

This patch affects w32fns.c and w32menu.c in what I
hope are trivial and safe ways, so I'm CC'ing this to
Eli to give him a heads-up too.