Work around wrong client size computation for not yet shown maximized windows.

Work around wrong client size computation for not yet shown maximized windows.

The client size of maximized windows which hadn't been shown yet isn't
computed correctly by wxMSW because WM_NCCALCSIZE returns too small values for
some reason. Attempts to fix this were unsuccessful so just ensure that the
window is re-laid out using the right size from WM_SIZE it receives when it is
shown instead of using the wrong pending size.

Closes #11762.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64115 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775