comctl32: comboex - fix some unintialized variables

[Dan Kegel]

You wrote:
> Fixes a compiler bug when using gcc-4.1

Wait- which is it, uninitialized variables (as your subject line
said), or a compiler bug (as your message said)?

If it's a compiler bug, which one?  Probably
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639, right?

Would setting the fields to any random value work as well?

Can we instead tell the compiler to avoid the bug?
(http://gcc.gnu.org/bugzilla/show_bug.cgi?id=9049
says there's no way yet to turn warnings on and off for
individual functions, sadly, but we can do it for individual files.)

A link to the bug report at gcc.gnu.org, and/or a wine wiki page about
the general issue, would be helpful.