After commit 2aa54a90, a double-byte
character is sent to the edit control by double WM_CHAR messages.
However, its WM_CHAR handler (ANSI version) can't process a double-
byte character properly because the handler converts WM_CHAR to WCHAR
one by one.
This fix queues the double-byte lead byte as it comes in and then uses
it afterwards for the WCHAR conversion.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=54337
(cherry picked from commit c385b647)