Add support for MDICREATESTRUCT conversion for 16-bit windows

[Dmitry Timoshkov]

"Alexandre Julliard" <julliard at winehq.org> wrote:

> Using GetExePtr is going to return the wrong instance once we get back
> to 16-bit code. The instance handles are actually not supposed to be
> converted at all, we just expand the 16-bit ones to 32-bit. What was
> the problem with your 16-bit app?

The app sends WM_MDICREATE message which fails with:
win.c,create_window_handle(): error 6 creating window

The WM_MDICREATE message gets translated from 16-bit to Ansi,
and the following CreateWindowEx calls fails due to bad hInstance
passed to create_window() server call.

-- 
Dmitry.