Ensure that runTest is not modal, even when a required module is not

Ensure that runTest is not modal, even when a required module is not
installed.

Create the code page small and hide it to reduce flicker, it will
later be shown and sized correctly when put into the notebook.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@28918 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775