Don't activate MSW dialogs when setting their initial size.

As the dialog is not shown yet at this moment, activating it didn't work
correctly and the dialog didn't get the focus when it was shown later.
Fix this by preventing ::SetWindowPos() from activating it, which it does by
default.

Closes #13765.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70036 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/toplevel.cpp

@@ -462,7 +462,7 @@ bool wxTopLevelWindowMSW::CreateDialog(const void *dlgTemplate,
         // Let the system position the window, just set its size.
         ::SetWindowPos(GetHwnd(), 0,
                        0, 0, w, h,
-                       SWP_NOMOVE | SWP_NOZORDER);
+                       SWP_NOMOVE | SWP_NOZORDER | SWP_NOACTIVATE);
     }
     else // Move the window to the desired location and set its size too.
     {