Better checks for wxMSWKeyboard::VKToWX() return value.

Better checks for wxMSWKeyboard::VKToWX() return value.

Don't generate key events without any valid key code (this shouldn't normally
happen but might on exotic keyboards with keys that we don't know about).

Also ensure that we can distinguish between VKToWX() returning dead keys and
non-Latin-1 keys by setting wchar_t output parameter to WXK_NONE too in the
former case but not the latter.

Generate wxEVT_CHAR_HOOK events for non-Latin-1 keys too in Unicode build.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65590 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775