This dialog was getting too tall, especially in the rich message boxes case, so reduce its vertical size. Also centre it on screen to prevent it from being displayed partially off it because contents was added to the dialog after creating it. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76255 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775