With the changes from 0b8db612.

With the changes from 9c8f8e71.

Signed-off-by: Nikolay Sivov <nsivov@codeweavers.com>

Check the content of the output buffer in addition to checking the
return value.
Also show that multibyte characters are not truncated when the output
buffer is too small.

wine_dbgstr_w() already quotes (and escapes) the string.

This slightly changes ime_ui_update_window to match what was previously
in winex11.drv, since e5f0cdfc, which
seems to be a more recent change.