When entering characters using IME on Windows, Japanese and Chinese
will both usually result in the first keystroke being duplicated. The
problem is that we are informed too late, after the first key is
pressed, that we are IME composing. This patch ensures we are entering
non-English characters using ImmGetConversionStatus() and then deals
with editing keys (like arrows and backspace) on a per-language basis.
see D11929 for more details.
Differential Revision: https://developer.blender.org/D11929
Reviewed by Brecht Van Lommel
836aeebf70