Display wxString in more readable way in MSVS debug visualizer.

Use "sb" format specifier to avoid having L"..." around the string and then
add just the quotes back manually.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76711 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775