Add a missing header with declaration of wxMessageBox() for PCH-less compilation. Closes #14376. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71646 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Add a missing header with declaration of wxMessageBox() for PCH-less compilation. Closes #14376. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71646 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775