MainFrame: destroy d3dfs window if vr is missing
MainFrame: make bExtOnTop visible to class
Don't drop out of fullscreen when loosing focus

Instead, unset the "on top" flag.
AboutDlg: recognize vs2013 update 2
Don't use GetSectionKey() in HasProfileEntry()

It creates section key if the section is missing.
Don't create empty section in settings migrator

"DVB configuration" was being created.