Fix generation of key events for non-alphabetic keys under Windows.

Fix generation of key events for non-alphabetic keys under Windows.

Don't hardcode the values of VK_OEM_XXX keys which are completely nonsensical
on keyboards with non-US layouts. Use the real unshifted value of the key as
its key code instead -- at least if it's a Latin-1 character. Otherwise, use
WXK_NONE as the key code and pass the character generated by the key as
Unicode character code.

Also generate WXK_NONE events for dead keys to avoid confusing them with the
corresponding normal key events.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65525 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775