user32: Preserve beginning of extra data for MDI windows.

[Sebastian Lackner]

On 26.02.2016 07:35, Marvin wrote:
> Hi,
> 
> While running your changed tests on Windows, I think I found new failures.
> Being a bot and all I'm not very good at pattern recognition, so I might be
> wrong, but could you please double-check?
> Full results can be found at
> https://testbot.winehq.org/JobDetails.pl?Key=20905
> 
> Your paranoid android.
> 
> 
> === w7u (32 bit msg) ===
> msg.c:8803: Test failed: did not get expected count for minimum timeout (54 != ~100).
> 
> === w1064 (32 bit msg) ===
> msg.c:6294: Test failed: Update region shouldn't be empty
> msg.c:6528: Test failed: InvalidateErase: 0: the msg sequence is not complete: expected 0085 - actual 0000
> msg.c:6530: Test failed: Paint: 0: the msg sequence is not complete: expected 000f - actual 0000
> msg.c:6300: Test failed: Regions are different
> msg.c:6300: Test failed: Regions are different
> msg.c:6300: Test failed: Regions are different
> 

The Win 7 test failure is random, the Win 10 test failures already existed before.