[USER32] DeferWindowPos accepts HWNDs with different parents

According to MSDN and tests, DeferWindowPos should be called with HWNDs that share the same parent, but calling it with a window that has a different parent doesn't fail on ReactOS and WINE, which is inconsistent with behavior on Windows.

Based on Tests by MuerteSeguraZ, DeferWindowPos doesn't fail on Windows and even EndDeferWindowPos returns TRUE, but GetLastError() reports ERROR_HWNDS_HAVE_DIFF_PARENT after calling EndDeferWindowPos and it doesn't move any window.