imm32: use SendMessage not PostMessage for the Default IME winproc

[Henri Verbeet]

On 6 November 2012 15:41, Aric Stewart <aric at codeweavers.com> wrote:
>
> This allows the calling program to properly get the return codes from the messages when they need them.
> Also prevent all of the calls for IME messages in that windproc from falling back through to DefWindowProc.
>
> for bug 32101

Can we have some tests for this, please? We already have a couple of
known deadlocks involving imm32 message processing, and based on the
amount of tests I'm not sure most of it is based on anything other
than "It seemed like a good idea at the time.".