CPack IFW: Support detecting IFW 4.1
Support auto-detecting Qt Installer Framework 4.1.
We could probably throw in 4.2 as well, but AFAICS, it is not available for macOS, so I'm not able to test that.
Support auto-detecting Qt Installer Framework 4.1.
We could probably throw in 4.2 as well, but AFAICS, it is not available for macOS, so I'm not able to test that.